Skip to Main Navigation
Skip to Page Content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Share This:
https://ntp.niehs.nih.gov/go/4530

TDMS Study 05185-04 Pathology Tables

NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55

                                                          CORE ANIMALS




       Facility:  I. I. T. Research Institute

       Chemical CAS #:  542-56-3

       Lock Date:  08/20/92

       Cage Range:  All

       Reasons For Removal:    25022 Accidently Killed                 25019 Moribund Sacrifice
                               25020 Natural Death                     25021 Terminal Sacrifice

       Removal Date Range:     All

       Treatment Groups:       Include All



























Note:  Animals arranged according to CID number

                                                              Page   1


NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 6| 5| 7| 6| 7| 0| 7| 6| 5| 7| 7|             
                             DAY ON TEST   | 3| 0| 2| 7| 3| 2| 3| 8| 2| 2| 2| 3| 3| 9| 9| 8| 3| 1| 2| 7| 3| 9| 8| 2| 2|             
                                           | 1| 9| 9| 2| 1| 9| 0| 9| 9| 9| 9| 1| 1| 0| 1| 5| 1| 3| 9| 1| 0| 1| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +|             
      Schwannoma Malignant, Metastatic,    |                                                                          |             
           Skin                            |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  A  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                            X                                             |             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  A  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  A  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  A  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocellular Carcinoma             |          X                                                        X      |             
      Hepatocellular Carcinoma, Multiple   |                                                                          |             
      Hepatocellular Adenoma               |                X                       X              X                 X|             
      Hepatocholangiocarcinoma             |                                           X                              |             
      Histiocytic Sarcoma                  |                                                                          |             
      Lymphoma Malignant Mixed             |                      X     X                 X     X                     |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                                 +                 +     +|             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                   X      |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocholangiocarcinoma, Metastatic,|                                                                          |             
           Liver                           |                                           X                              |             
      Lymphoma Malignant Mixed             |                      X     X                       X                     |             
      Schwannoma Malignant, Metastatic,    |                                                                          |             
           Skin                            |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                            X                       X                     |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                    X                     |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocholangiocarcinoma, Metastatic,|                                                                          |             
           Liver                           |                                           X                              |             
      Lymphoma Malignant Mixed             |                      X                             X                     |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                      X                             X                     |             
      Capsule, Lymphoma Malignant Mixed    |                      X                                                   |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   2                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 6| 5| 7| 6| 7| 0| 7| 6| 5| 7| 7|             
                             DAY ON TEST   | 3| 0| 2| 7| 3| 2| 3| 8| 2| 2| 2| 3| 3| 9| 9| 8| 3| 1| 2| 7| 3| 9| 8| 2| 2|             
                                           | 1| 9| 9| 2| 1| 9| 0| 9| 9| 9| 9| 1| 1| 0| 1| 5| 1| 3| 9| 1| 0| 1| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                      X                             X                     |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                  +                                       |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  M  +  M  M  +  +  M  +  +  M  +  M  M  M  M  +  M  +  M  +  +  M  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  M|             
      Pars Distalis, Adenoma               | X     X        X  X           X           X     X                    X   |             
      Pars Intermedia, Adenoma             |       X                                                                  |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Adenoma             | X     X                                                                  |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +|             
      Cystadenoma                          |                                  X                                       |             
      Lymphoma Malignant Mixed             |                      X                             X                     |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangioma                           |                                                                          |             
      Histiocytic Sarcoma                  |                                                                          |             
      Lymphoma Malignant Mixed             |                      X                                                   |             
      Polyp Stromal                        |                                  X                                       |             
      Sarcoma Stromal                      |                            X                                             |             
                                            __________________________________________________________________________|             
   Vagina                                  |                                                                          |             
      Histiocytic Sarcoma                  |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                      X                                                   |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                      +                    +        +                     |             
      Inguinal, Histiocytic Sarcoma        |                                                                          |             
      Lumbar, Histiocytic Sarcoma          |                                                                          |             
      Lumbar, Lymphoma Malignant Mixed     |                      X                             X                     |             
      Pancreatic, Hepatocholangiocarcinoma,|                                                                          |             
           Metastatic, Liver               |                                           X                              |             
      Renal, Histiocytic Sarcoma           |                                                                          |             
      Renal, Lymphoma Malignant Mixed      |                      X                             X                     |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  +  M  +  +  M  M  +  +  M  +  +  M  M  M  +  +  +  +  M  M  +  M  M|             
      Lymphoma Malignant Mixed             |                            X                       X                     |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                                                                          |             
      Lymphoma Malignant Mixed             |                      X     X                       X                     |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                      X     X                       X                     |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   3                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 6| 5| 7| 6| 7| 0| 7| 6| 5| 7| 7|             
                             DAY ON TEST   | 3| 0| 2| 7| 3| 2| 3| 8| 2| 2| 2| 3| 3| 9| 9| 8| 3| 1| 2| 7| 3| 9| 8| 2| 2|             
                                           | 1| 9| 9| 2| 1| 9| 0| 9| 9| 9| 9| 1| 1| 0| 1| 5| 1| 3| 9| 1| 0| 1| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                                                                          |             
      Lymphoma Malignant Mixed             |                      X                             X                     |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangiosarcoma                      |                                        X                                 |             
      Histiocytic Sarcoma                  |                                                                          |             
      Lymphoma Malignant Mixed             |                      X     X                 X     X                     |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                      X     X                       X                     |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcutaneous Tissue, Hemangioma      |                                                                          |             
      Subcutaneous Tissue, Sarcoma         |       X                                                                  |             
      Subcutaneous Tissue, Schwannoma      |                                                                          |             
          Malignant                        |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Schwannoma Malignant, Metastatic,    |                                                                          |             
           Skin                            |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         |             X        X              X                                    |             
      Alveolar/Bronchiolar Carcinoma       |                                        X                                 |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                   X      |             
      Hepatocholangiocarcinoma, Metastatic,|                                                                          |             
           Liver                           |                                           X                              |             
      Lymphoma Malignant Mixed             |                      X     X                       X                     |             
      Mediastinum,                         |                                                                          |             
          Hepatocholangiocarcinoma,        |                                                                          |             
          Metastatic, Liver                |                                           X                              |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   4                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 7| 7| 6| 7| 7| 7| 7| 7| 6| 6| 5| 7| 6| 7| 0| 7| 6| 5| 7| 7|             
                             DAY ON TEST   | 3| 0| 2| 7| 3| 2| 3| 8| 2| 2| 2| 3| 3| 9| 9| 8| 3| 1| 2| 7| 3| 9| 8| 2| 2|             
                                           | 1| 9| 9| 2| 1| 9| 0| 9| 9| 9| 9| 1| 1| 0| 1| 5| 1| 3| 9| 1| 0| 1| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                      X     X                       X                     |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Histiocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                      X     X                       X                     |             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                                                                          |             
      Lymphoma Malignant Histiocytic       |                                                                          |             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                      X     X                 X     X                     |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   5                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 7| 7| 6| 6| 7|             
                             DAY ON TEST   | 3| 3| 2| 3| 7| 0| 2| 3| 3| 3| 2| 3| 3| 3| 3| 2| 3| 9| 3| 4| 2| 3| 9| 4| 3|             
                                           | 0| 1| 9| 8| 6| 9| 9| 0| 0| 5| 9| 0| 0| 0| 1| 9| 1| 5| 0| 9| 9| 0| 6| 3| 1|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    CONTROL                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
      Schwannoma Malignant, Metastatic,    |                                                                          |             
           Skin                            |                X                                                         |             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  A  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  A  +  +  +  A  +  +  +  +  +  +  +  M  +  +  +  +  A  A  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  +  A  A  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocellular Carcinoma             |                                     X                                    |             
      Hepatocellular Carcinoma, Multiple   |                                                                   X      |             
      Hepatocellular Adenoma               |                      X                 X                                 |             
      Hepatocholangiocarcinoma             |                                                                          |             
      Histiocytic Sarcoma                  |             X                                                        X   |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                   +     +                       +  +                     |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocholangiocarcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
      Schwannoma Malignant, Metastatic,    |                                                                          |             
           Skin                            |                X                                                         |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocholangiocarcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
      Capsule, Lymphoma Malignant Mixed    |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   6                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 7| 7| 6| 6| 7|             
                             DAY ON TEST   | 3| 3| 2| 3| 7| 0| 2| 3| 3| 3| 2| 3| 3| 3| 3| 2| 3| 9| 3| 4| 2| 3| 9| 4| 3|             
                                           | 0| 1| 9| 8| 6| 9| 9| 0| 0| 5| 9| 0| 0| 0| 1| 9| 1| 5| 0| 9| 9| 0| 6| 3| 1|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    CONTROL                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  M  +        +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                 +                        |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  M  M  M  M  +  +  +  M  M  +  M  +  +  M  M  M  M  M  +  M  +  M  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
      Pars Distalis, Adenoma               |          X                 X                 X                 X         |             
      Pars Intermedia, Adenoma             |                                                             X            |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Adenoma             |                                                          X  X            |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
      Cystadenoma                          |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangioma                           |                X                                                         |             
      Histiocytic Sarcoma                  |             X                                                        X   |             
      Lymphoma Malignant Mixed             |                                                                          |             
      Polyp Stromal                        | X                 X                                                      |             
      Sarcoma Stromal                      |                                                                          |             
                                            __________________________________________________________________________|             
   Vagina                                  |                                                                      +   |             
      Histiocytic Sarcoma                  |                                                                      X   |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                                                      +   |             
      Inguinal, Histiocytic Sarcoma        |                                                                      X   |             
      Lumbar, Histiocytic Sarcoma          |                                                                      X   |             
      Lumbar, Lymphoma Malignant Mixed     |                                                                          |             
      Pancreatic, Hepatocholangiocarcinoma,|                                                                          |             
           Metastatic, Liver               |                                                                          |             
      Renal, Histiocytic Sarcoma           |                                                                      X   |             
      Renal, Lymphoma Malignant Mixed      |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  +  M  M  M  +  +  +  M  +  M  M  M  M  M  M  M  M  M  M  M  M  M  M|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  M  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                                                                      X   |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                               X                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   7                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 7| 7| 6| 6| 7|             
                             DAY ON TEST   | 3| 3| 2| 3| 7| 0| 2| 3| 3| 3| 2| 3| 3| 3| 3| 2| 3| 9| 3| 4| 2| 3| 9| 4| 3|             
                                           | 0| 1| 9| 8| 6| 9| 9| 0| 0| 5| 9| 0| 0| 0| 1| 9| 1| 5| 0| 9| 9| 0| 6| 3| 1|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    CONTROL                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                                                                      X   |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangiosarcoma                      |                                                                          |             
      Histiocytic Sarcoma                  |                                                                      X   |             
      Lymphoma Malignant Mixed             |                               X                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                              X                           |             
      Lymphoma Malignant Mixed             |                               X                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcutaneous Tissue, Hemangioma      | X                                                                        |             
      Subcutaneous Tissue, Sarcoma         |                                                                          |             
      Subcutaneous Tissue, Schwannoma      |                                                                          |             
          Malignant                        |                X                                                         |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Schwannoma Malignant, Metastatic,    |                                                                          |             
           Skin                            |                X                                                         |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         |                                                 X                        |             
      Alveolar/Bronchiolar Carcinoma       |                                                             X            |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                          |             
      Hepatocholangiocarcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
      Mediastinum,                         |                                                                          |             
          Hepatocholangiocarcinoma,        |                                                                          |             
          Metastatic, Liver                |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   8                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 6| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 5| 7| 6| 7| 7| 6| 6| 7|             
                             DAY ON TEST   | 3| 3| 2| 3| 7| 0| 2| 3| 3| 3| 2| 3| 3| 3| 3| 2| 3| 9| 3| 4| 2| 3| 9| 4| 3|             
                                           | 0| 1| 9| 8| 6| 9| 9| 0| 0| 5| 9| 0| 0| 0| 1| 9| 1| 5| 0| 9| 9| 0| 6| 3| 1|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    CONTROL                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  A  +  +|             
      Lymphoma Malignant Histiocytic       |                                                                      X   |             
      Lymphoma Malignant Mixed             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |             X                                                        X   |             
      Lymphoma Malignant Histiocytic       |                                                                      X   |             
      Lymphoma Malignant Lymphocytic       |                                              X                           |             
      Lymphoma Malignant Mixed             |                               X                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page   9                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 0|                                                                       |            |
                             DAY ON TEST   | 9|                                                                       |            |
                                           | 1|                                                                       |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0|                                                                       |     O      |
   B6C3F1 MICE FEMALE                      | 0|                                                                       |     T      |
                               ANIMAL ID   | 1|                                                                       |     A      |
    CONTROL                                | 1|                                                                       |     L      |
                                           | 5|                                                                       |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +                                                                        |  51        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | A                                                                        |  46        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +                                                                        |  51        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +                                                                        |  48        |
      Schwannoma Malignant, Metastatic,    |                                                                          |            |
           Skin                            |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +                                                                        |  48        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | A                                                                        |  42        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | A                                                                        |  44        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +                                                                        |  44        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +                                                                        |  51        |
      Hepatocellular Carcinoma             |                                                                          |          3 |
      Hepatocellular Carcinoma, Multiple   |                                                                          |          1 |
      Hepatocellular Adenoma               |                                                                          |          6 |
      Hepatocholangiocarcinoma             |                                                                          |          1 |
      Histiocytic Sarcoma                  |                                                                          |          2 |
      Lymphoma Malignant Mixed             |                                                                          |          4 |
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   7        |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +                                                                        |  51        |
      Hepatocholangiocarcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          3 |
      Schwannoma Malignant, Metastatic,    |                                                                          |            |
           Skin                            |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +                                                                        |  51        |
      Lymphoma Malignant Mixed             |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +                                                                        |  51        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +                                                                        |  51        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Tooth                                   | +                                                                        |   1        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +                                                                        |  51        |
      Hepatocholangiocarcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          2 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  10                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 0|                                                                       |            |
                             DAY ON TEST   | 9|                                                                       |            |
                                           | 1|                                                                       |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0|                                                                       |     O      |
   B6C3F1 MICE FEMALE                      | 0|                                                                       |     T      |
                               ANIMAL ID   | 1|                                                                       |     A      |
    CONTROL                                | 1|                                                                       |     L      |
                                           | 5|                                                                       |            |
 __________________________________________________________________________________________________________________________________ 
 CARDIOVASCULAR SYSTEM - cont              |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +                                                                        |  50        |
      Lymphoma Malignant Mixed             |                                                                          |          2 |
      Capsule, Lymphoma Malignant Mixed    |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +                                                                        |  47        |
      Lymphoma Malignant Mixed             |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   2        |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +                                                                        |  21        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +                                                                        |  48        |
      Pars Distalis, Adenoma               |                                                                          |         12 |
      Pars Intermedia, Adenoma             |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +                                                                        |  51        |
      Follicular Cell, Adenoma             |                                                                          |          4 |
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Ovary                                   | +                                                                        |  49        |
      Cystadenoma                          |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Uterus                                  | +                                                                        |  51        |
      Hemangioma                           |                                                                          |          1 |
      Histiocytic Sarcoma                  |                                                                          |          2 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Polyp Stromal                        |                                                                          |          3 |
      Sarcoma Stromal                      |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Vagina                                  |                                                                          |   1        |
      Histiocytic Sarcoma                  |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +                                                                        |  51        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   4        |
      Inguinal, Histiocytic Sarcoma        |                                                                          |          1 |
      Lumbar, Histiocytic Sarcoma          |                                                                          |          1 |
      Lumbar, Lymphoma Malignant Mixed     |                                                                          |          2 |
      Pancreatic, Hepatocholangiocarcinoma,|                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  11                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 0|                                                                       |            |
                             DAY ON TEST   | 9|                                                                       |            |
                                           | 1|                                                                       |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0|                                                                       |     O      |
   B6C3F1 MICE FEMALE                      | 0|                                                                       |     T      |
                               ANIMAL ID   | 1|                                                                       |     A      |
    CONTROL                                | 1|                                                                       |     L      |
                                           | 5|                                                                       |            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
           Metastatic, Liver               |                                                                          |          1 |
      Renal, Histiocytic Sarcoma           |                                                                          |          1 |
      Renal, Lymphoma Malignant Mixed      |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +                                                                        |  20        |
      Lymphoma Malignant Mixed             |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +                                                                        |  49        |
      Histiocytic Sarcoma                  |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          3 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +                                                                        |  51        |
      Lymphoma Malignant Mixed             |                                                                          |          4 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +                                                                        |  49        |
      Histiocytic Sarcoma                  |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +                                                                        |  51        |
      Hemangiosarcoma                      |                                                                          |          1 |
      Histiocytic Sarcoma                  |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          5 |
                                            __________________________________________________________________________|____________|
   Thymus                                  | M                                                                        |  47        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          4 |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +                                                                        |  49        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +                                                                        |  51        |
      Subcutaneous Tissue, Hemangioma      |                                                                          |          1 |
      Subcutaneous Tissue, Sarcoma         |                                                                          |          1 |
      Subcutaneous Tissue, Schwannoma      |                                                                          |            |
          Malignant                        |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +                                                                        |  51        |
      Schwannoma Malignant, Metastatic,    |                                                                          |            |
           Skin                            |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | M                                                                        |  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +                                                                        |  51        |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  12                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 0|                                                                       |            |
                             DAY ON TEST   | 9|                                                                       |            |
                                           | 1|                                                                       |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0|                                                                       |     O      |
   B6C3F1 MICE FEMALE                      | 0|                                                                       |     T      |
                               ANIMAL ID   | 1|                                                                       |     A      |
    CONTROL                                | 1|                                                                       |     L      |
                                           | 5|                                                                       |            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Lung                                    | +                                                                        |  51        |
      Alveolar/Bronchiolar Adenoma         |                                                                          |          4 |
      Alveolar/Bronchiolar Carcinoma       |                                                                          |          2 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                                                          |          1 |
      Hepatocholangiocarcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          3 |
      Mediastinum,                         |                                                                          |            |
          Hepatocholangiocarcinoma,        |                                                                          |            |
          Metastatic, Liver                |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Nose                                    | +                                                                        |  51        |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +                                                                        |  51        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +                                                                        |  51        |
      Lymphoma Malignant Mixed             |                                                                          |          3 |
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +                                                                        |  49        |
      Lymphoma Malignant Histiocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          3 |
 __________________________________________________________________________________________________________________________________ 
 SYSTEMIC LESIONS                          |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Multiple Organs                         | +                                                                        |  51        |
      Histiocytic Sarcoma                  |                                                                          |          2 |
      Lymphoma Malignant Histiocytic       |                                                                          |          1 |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          5 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  13                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 2| 9| 3| 3| 3| 3| 2| 2| 3| 2| 2| 3| 0| 2| 3| 3| 1| 4| 2| 3| 2| 3| 3| 3|             
                                           | 1| 9| 7| 0| 1| 1| 1| 9| 0| 1| 9| 8| 0| 7| 9| 0| 0| 4| 5| 9| 1| 9| 0| 1| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 8| 8| 8| 8| 8| 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Squamous Cell Carcinoma              |                                                                      X   |             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  M|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocellular Carcinoma             |                            X           X                                 |             
      Hepatocellular Adenoma               |                      X     X                 X                          X|             
      Histiocytic Sarcoma                  |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                         X                             X                  |             
                                            __________________________________________________________________________|             
   Mesentery                               | +     +              +                                                   |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +     +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
      Pheochromocytoma Malignant           |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                                          |             
      Adenoma                              |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  M  M  +  M  M  M  +  M  +  +  +  +  M  +  +  M  M  M  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +|             
      Pars Distalis, Adenoma               |                   X        X  X                          X        X  X  X|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  14                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 2| 9| 3| 3| 3| 3| 2| 2| 3| 2| 2| 3| 0| 2| 3| 3| 1| 4| 2| 3| 2| 3| 3| 3|             
                                           | 1| 9| 7| 0| 1| 1| 1| 9| 0| 1| 9| 8| 0| 7| 9| 0| 0| 4| 5| 9| 1| 9| 0| 1| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 8| 8| 8| 8| 8| 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
      Pars Intermedia, Adenoma             |                            X     X                                       |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Adenoma             |                                     X     X                              |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |                                                                          |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Deciduoma NOS                        |                                                                          |             
      Histiocytic Sarcoma                  |                                                                          |             
      Polyp Stromal                        |                X                                                         |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Lymph Node                              |    +  +                 +                       +                        |             
      Lumbar, Lymphoma Malignant           |                                                                          |             
          Undifferentiated Cell Type       |                         X                                                |             
      Renal, Lymphoma Malignant            |                                                                          |             
          Undifferentiated Cell Type       |                         X                                                |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  M  +  +  +  +  +  +  +  +  +  M  M  +  +  M  M  M  M  +  M  +  M  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                         X                                                |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  M  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  M  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                         X                             X                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | M  +  +  M  +  +  +  +  +  +  +  +  +  +  M  M  +  +  +  +  +  +  M  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                         X                             X                  |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  15                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 2| 9| 3| 3| 3| 3| 2| 2| 3| 2| 2| 3| 0| 2| 3| 3| 1| 4| 2| 3| 2| 3| 3| 3|             
                                           | 1| 9| 7| 0| 1| 1| 1| 9| 0| 1| 9| 8| 0| 7| 9| 0| 0| 4| 5| 9| 1| 9| 0| 1| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 8| 8| 8| 8| 8| 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Hemangiosarcoma                      |                                                                X         |             
      Lymphoma Malignant Mixed             |          X                                                               |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                         X                             X                  |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                         X                                                |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcutaneous Tissue, Hemangiosarcoma | X                                                                        |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangioma                           |                                                 X                        |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                    +                     |             
      Hemangiosarcoma                      |                                                                          |             
      Osteosarcoma                         |                                                    X                     |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         |                   X                                                      |             
      Alveolar/Bronchiolar Adenoma,        |                                                                          |             
          Multiple                         |             X                                                        X   |             
      Alveolar/Bronchiolar Carcinoma       |                            X                                             |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                            X                                             |             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                         X                             X                  |             
      Osteosarcoma, Metastatic, Skeletal   |                                                                          |             
          Muscle                           |                                                    X                     |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |       +                                                                  |             
      Adenoma                              |       X                                                                  |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  16                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 6| 7| 7| 7| 7| 7| 5| 7| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 3| 2| 9| 3| 3| 3| 3| 2| 2| 3| 2| 2| 3| 0| 2| 3| 3| 1| 4| 2| 3| 2| 3| 3| 3|             
                                           | 1| 9| 7| 0| 1| 1| 1| 9| 0| 1| 9| 8| 0| 7| 9| 0| 0| 4| 5| 9| 1| 9| 0| 1| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 8| 8| 8| 8| 8| 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                         X                                                |             
      Osteosarcoma, Metastatic, Skeletal   |                                                                          |             
          Muscle                           |                                                    X                     |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                                                                          |             
      Lymphoma Malignant Mixed             |          X                                                               |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                         X                             X                  |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  17                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 2| 2| 3| 2| 2| 3| 3| 2| 3| 8| 1| 2| 3| 3| 3| 3| 2| 2| 3| 2| 2| 2|             
                                           | 9| 9| 0| 9| 9| 1| 9| 9| 1| 0| 9| 0| 6| 2| 9| 0| 0| 0| 1| 9| 9| 0| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Squamous Cell Carcinoma              |                                                                          |             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocellular Carcinoma             |                   X                                      X               |             
      Hepatocellular Adenoma               | X     X                 X                       X     X     X            |             
      Histiocytic Sarcoma                  |                                           X                              |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                  +                                       |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                 X                        |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +     +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
      Pheochromocytoma Malignant           |                                        X                                 |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                          +        +      |             
      Adenoma                              |                                                          X               |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  M  +  M  +  +  +  +  +  +  +  M  M  +  M  M  +  +  +  M  M  M  M  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  I  +  +  +  +  +  +  +|             
      Pars Distalis, Adenoma               |    X           X  X  X  X  X  X  X           X        X  X  X            |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  18                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 2| 2| 3| 2| 2| 3| 3| 2| 3| 8| 1| 2| 3| 3| 3| 3| 2| 2| 3| 2| 2| 2|             
                                           | 9| 9| 0| 9| 9| 1| 9| 9| 1| 0| 9| 0| 6| 2| 9| 0| 0| 0| 1| 9| 9| 0| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
      Pars Intermedia, Adenoma             |                                                                          |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Adenoma             |                                                                   X      |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |                                                                   +      |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                 X                        |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Deciduoma NOS                        |                                           X                              |             
      Histiocytic Sarcoma                  |                X                          X                              |             
      Polyp Stromal                        |                                           X                              |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                 X                        |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                     +                                    |             
      Lumbar, Lymphoma Malignant           |                                                                          |             
          Undifferentiated Cell Type       |                                                                          |             
      Renal, Lymphoma Malignant            |                                                                          |             
          Undifferentiated Cell Type       |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  +  +  +  M  M  +  M  +  M  +  +  M  +  +  +  M  M|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                 X                        |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                 X                        |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                 X                        |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  19                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 2| 2| 3| 2| 2| 3| 3| 2| 3| 8| 1| 2| 3| 3| 3| 3| 2| 2| 3| 2| 2| 2|             
                                           | 9| 9| 0| 9| 9| 1| 9| 9| 1| 0| 9| 0| 6| 2| 9| 0| 0| 0| 1| 9| 9| 0| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Hemangiosarcoma                      |                                                                          |             
      Lymphoma Malignant Mixed             |                                                 X        X               |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  M  +  +  +  +  +  +  M  M  +  +  +  +  +  +  +  M  +  +  +|             
      Lymphoma Malignant Mixed             |                                                 X                        |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcutaneous Tissue, Hemangiosarcoma |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangioma                           |                                                                          |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |    +                                                           +         |             
      Hemangiosarcoma                      |                                                                X         |             
      Osteosarcoma                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         |          X     X  X        X  X  X           X     X  X     X        X   |             
      Alveolar/Bronchiolar Adenoma,        |                                                                          |             
          Multiple                         |                                                                          |             
      Alveolar/Bronchiolar Carcinoma       |                X                                                         |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                          |             
      Lymphoma Malignant Mixed             |                                                 X                        |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
      Osteosarcoma, Metastatic, Skeletal   |                                                                          |             
          Muscle                           |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                          |             
      Adenoma                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  20                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 2| 2| 3| 2| 2| 3| 3| 2| 3| 8| 1| 2| 3| 3| 3| 3| 2| 2| 3| 2| 2| 2|             
                                           | 9| 9| 0| 9| 9| 1| 9| 9| 1| 0| 9| 0| 6| 2| 9| 0| 0| 0| 1| 9| 9| 0| 9| 9| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    37.5 PPM                               | 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 3|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                      X                                                   |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
      Osteosarcoma, Metastatic, Skeletal   |                                                                          |             
          Muscle                           |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                X                          X                              |             
      Lymphoma Malignant Mixed             |                      X                          X        X               |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  21                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 1|                                                                       |            |
                             DAY ON TEST   | 8|                                                                       |            |
                                           | 3|                                                                       |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0|                                                                       |     O      |
   B6C3F1 MICE FEMALE                      | 0|                                                                       |     T      |
                               ANIMAL ID   | 2|                                                                       |     A      |
    37.5 PPM                               | 4|                                                                       |     L      |
                                           | 0|                                                                       |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +                                                                        |  50        |
      Squamous Cell Carcinoma              |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +                                                                        |  47        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +                                                                        |  51        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +                                                                        |  51        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | A                                                                        |  49        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | A                                                                        |  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | M                                                                        |  50        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | A                                                                        |  48        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +                                                                        |  51        |
      Hepatocellular Carcinoma             |                                                                          |          4 |
      Hepatocellular Adenoma               |                                                                          |         10 |
      Histiocytic Sarcoma                  |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   4        |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +                                                                        |  51        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +                                                                        |  51        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +                                                                        |  51        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +                                                                        |  51        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +                                                                        |  51        |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +                                                                        |  51        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +                                                                        |  49        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
      Pheochromocytoma Malignant           |                                                                          |          1 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  22                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 1|                                                                       |            |
                             DAY ON TEST   | 8|                                                                       |            |
                                           | 3|                                                                       |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0|                                                                       |     O      |
   B6C3F1 MICE FEMALE                      | 0|                                                                       |     T      |
                               ANIMAL ID   | 2|                                                                       |     A      |
    37.5 PPM                               | 4|                                                                       |     L      |
                                           | 0|                                                                       |            |
 __________________________________________________________________________________________________________________________________ 
 ENDOCRINE SYSTEM - cont                   |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   2        |
      Adenoma                              |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +                                                                        |  29        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +                                                                        |  48        |
      Pars Distalis, Adenoma               |                                                                          |         19 |
      Pars Intermedia, Adenoma             |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +                                                                        |  51        |
      Follicular Cell, Adenoma             |                                                                          |          3 |
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Ovary                                   | +                                                                        |  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Uterus                                  | +                                                                        |  51        |
      Deciduoma NOS                        |                                                                          |          1 |
      Histiocytic Sarcoma                  |                                                                          |          2 |
      Polyp Stromal                        |                                                                          |          2 |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +                                                                        |  51        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   5        |
      Lumbar, Lymphoma Malignant           |                                                                          |            |
          Undifferentiated Cell Type       |                                                                          |          1 |
      Renal, Lymphoma Malignant            |                                                                          |            |
          Undifferentiated Cell Type       |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | M                                                                        |  34        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +                                                                        |  48        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  23                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 1|                                                                       |            |
                             DAY ON TEST   | 8|                                                                       |            |
                                           | 3|                                                                       |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0|                                                                       |     O      |
   B6C3F1 MICE FEMALE                      | 0|                                                                       |     T      |
                               ANIMAL ID   | 2|                                                                       |     A      |
    37.5 PPM                               | 4|                                                                       |     L      |
                                           | 0|                                                                       |            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | A                                                                        |  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +                                                                        |  44        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +                                                                        |  51        |
      Hemangiosarcoma                      |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          3 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Thymus                                  | +                                                                        |  47        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +                                                                        |  51        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +                                                                        |  51        |
      Subcutaneous Tissue, Hemangiosarcoma |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +                                                                        |  51        |
      Hemangioma                           |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                                                                          |   3        |
      Hemangiosarcoma                      |                                                                          |          1 |
      Osteosarcoma                         |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +                                                                        |  51        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +                                                                        |  49        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +                                                                        |  51        |
      Alveolar/Bronchiolar Adenoma         |                                                                          |         12 |
      Alveolar/Bronchiolar Adenoma,        |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  24                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 1|                                                                       |            |
                             DAY ON TEST   | 8|                                                                       |            |
                                           | 3|                                                                       |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0|                                                                       |     O      |
   B6C3F1 MICE FEMALE                      | 0|                                                                       |     T      |
                               ANIMAL ID   | 2|                                                                       |     A      |
    37.5 PPM                               | 4|                                                                       |     L      |
                                           | 0|                                                                       |            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
          Multiple                         |                                                                          |          2 |
      Alveolar/Bronchiolar Carcinoma       |                                                                          |          2 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          2 |
      Osteosarcoma, Metastatic, Skeletal   |                                                                          |            |
          Muscle                           |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Nose                                    | +                                                                        |  51        |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +                                                                        |  51        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   1        |
      Adenoma                              |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +                                                                        |  51        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
      Osteosarcoma, Metastatic, Skeletal   |                                                                          |            |
          Muscle                           |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +                                                                        |  50        |
 __________________________________________________________________________________________________________________________________ 
 SYSTEMIC LESIONS                          |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Multiple Organs                         | +                                                                        |  51        |
      Histiocytic Sarcoma                  |                                                                          |          2 |
      Lymphoma Malignant Mixed             |                                                                          |          4 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          2 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  25                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 4| 7| 4| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 6| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 3| 2| 3| 3| 6| 2| 1| 3| 3| 3| 2| 3| 2| 6| 3| 5| 3| 6| 2| 0| 3| 3|             
                                           | 9| 9| 0| 1| 9| 4| 1| 0| 8| 9| 1| 0| 0| 9| 0| 9| 3| 0| 8| 0| 0| 9| 6| 0| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocellular Carcinoma             |                   X           X                                          |             
      Hepatocellular Adenoma               |                   X                       X                              |             
      Hepatocellular Adenoma, Multiple     |                               X  X                                       |             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                   X      |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Mesentery                               |                         +                                                |             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                X         |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                X         |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  26                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 4| 7| 4| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 6| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 3| 2| 3| 3| 6| 2| 1| 3| 3| 3| 2| 3| 2| 6| 3| 5| 3| 6| 2| 0| 3| 3|             
                                           | 9| 9| 0| 1| 9| 4| 1| 0| 8| 9| 1| 0| 0| 9| 0| 9| 3| 0| 8| 0| 0| 9| 6| 0| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM - cont                  |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
      Odontoma                             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +     +  +     +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
      Pheochromocytoma Benign              |                                           X                              |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                      +        +                             +            |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  M  M  M  +  M  M  M  +  +  +  +  +  +  +  M  +  M  +  +  +  M  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pars Distalis, Adenoma               |          X                             X  X        X     X     X  X     X|             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Adenoma             |                                                                         X|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |                                     +                                    |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|             
      Cystadenoma                          |                                                 X                        |             
      Granulosa Cell Tumor Malignant       |                                                                          |             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                   X      |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Oviduct                                 |                         +                                                |             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Leiomyosarcoma                       |                                                    X                     |             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Vagina                                  |                         +                                                |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  27                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 4| 7| 4| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 6| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 3| 2| 3| 3| 6| 2| 1| 3| 3| 3| 2| 3| 2| 6| 3| 5| 3| 6| 2| 0| 3| 3|             
                                           | 9| 9| 0| 1| 9| 4| 1| 0| 8| 9| 1| 0| 0| 9| 0| 9| 3| 0| 8| 0| 0| 9| 6| 0| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Lymph Node                              |             +  +                                      +           +      |             
      Iliac, Lymphoma Malignant Mixed      |                                                                   X      |             
      Inguinal, Lymphoma Malignant         |                                                                          |             
          Undifferentiated Cell Type       |                                                       X                  |             
      Lumbar, Lymphoma Malignant Mixed     |                                                                          |             
      Lumbar, Lymphoma Malignant           |                                                                          |             
          Undifferentiated Cell Type       |                                                       X                  |             
      Renal, Lymphoma Malignant Mixed      |                                                                   X      |             
      Renal, Lymphoma Malignant            |                                                                          |             
          Undifferentiated Cell Type       |                                                       X                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  +  +  M  +  M  +  +  M  M  +  +  +  +  +  M  +  +  +  M  M  +  M  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                   X      |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                X  X      |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                   X      |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                X  X      |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                           X                       X      |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                X  X      |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  28                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 4| 7| 4| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 6| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 3| 2| 3| 3| 6| 2| 1| 3| 3| 3| 2| 3| 2| 6| 3| 5| 3| 6| 2| 0| 3| 3|             
                                           | 9| 9| 0| 1| 9| 4| 1| 0| 8| 9| 1| 0| 0| 9| 0| 9| 3| 0| 8| 0| 0| 9| 6| 0| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Adenocarcinoma                       |                                                                          |             
      Adenoma                              |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcutaneous Tissue, Fibrosarcoma    |                X                                                         |             
      Subcutaneous Tissue, Sarcoma         |                                     X                                    |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Adenoma                              |                                                                          |             
      Alveolar/Bronchiolar Adenoma         |       X                       X                                         X|             
      Alveolar/Bronchiolar Adenoma,        |                                                                          |             
          Multiple                         |                                                                          |             
      Alveolar/Bronchiolar Carcinoma       | X                                                                        |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                   X           X                                          |             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
      Mediastinum, Hepatocellular          |                                                                          |             
          Carcinoma, Metastatic, Liver     |                               X                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                          |             
      Adenoma                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  29                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 7| 4| 7| 4| 6| 7| 7| 7| 7| 7| 7| 7| 6| 7| 5| 7| 6| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 3| 3| 2| 3| 3| 6| 2| 1| 3| 3| 3| 2| 3| 2| 6| 3| 5| 3| 6| 2| 0| 3| 3|             
                                           | 9| 9| 0| 1| 9| 4| 1| 0| 8| 9| 1| 0| 0| 9| 0| 9| 3| 0| 8| 0| 0| 9| 6| 0| 0|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    75 PPM                                 | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                          |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                                                X  X      |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                         X                                                |             
      Lymphoma Malignant Mixed             |                                           X                    X  X      |             
      Lymphoma Malignant Undifferentiated  |                                                                          |             
          Cell Type                        |                                                       X                  |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  30                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 7| 7| 7| 4| 7| 7| 6| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 2|            |
                             DAY ON TEST   | 3| 3| 3| 2| 3| 1| 3| 3| 3| 8| 3| 3| 3| 2| 2| 2| 2| 3| 2| 2| 2| 3| 2| 5| 1|            |
                                           | 0| 6| 0| 9| 1| 5| 0| 0| 9| 5| 0| 1| 0| 9| 9| 9| 9| 0| 9| 9| 9| 0| 9| 8| 0|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|     A      |
    75 PPM                                 | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 0| 5|            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | M  +  +  +  +  A  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  A|  45        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hepatocellular Carcinoma             |                                                                          |          2 |
      Hepatocellular Adenoma               |                                                                          |          2 |
      Hepatocellular Adenoma, Multiple     | X                                   X  X                                 |          5 |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             | X        X  X                 X                                          |          5 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Mesentery                               |                               +                                   +      |   3        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                       X                  |          2 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  31                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 7| 7| 7| 4| 7| 7| 6| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 2|            |
                             DAY ON TEST   | 3| 3| 3| 2| 3| 1| 3| 3| 3| 8| 3| 3| 3| 2| 2| 2| 2| 3| 2| 2| 2| 3| 2| 5| 1|            |
                                           | 0| 6| 0| 9| 1| 5| 0| 0| 9| 5| 0| 1| 0| 9| 9| 9| 9| 0| 9| 9| 9| 0| 9| 8| 0|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|     A      |
    75 PPM                                 | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 0| 5|            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM - cont                  |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Tooth                                   |                                                    +                     |   1        |
      Odontoma                             |                                                    X                     |          1 |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         |    +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M|  45        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
      Pheochromocytoma Benign              |                                                       X                  |          2 |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   3        |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  M  +  +  +  +  +  M  M  +  +  M  +  M  M  +  M  +  +  +  +  +|  33        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Pars Distalis, Adenoma               |             X        X     X     X  X  X     X  X        X  X            |         18 |
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Follicular Cell, Adenoma             |                                                                X         |          2 |
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          |                                                                         +|   2        |
                                            __________________________________________________________________________|____________|
   Ovary                                   | M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|  46        |
      Cystadenoma                          |                                                             X            |          2 |
      Granulosa Cell Tumor Malignant       |                                                                         X|          1 |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |             X                                                            |          2 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  32                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 7| 7| 7| 4| 7| 7| 6| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 2|            |
                             DAY ON TEST   | 3| 3| 3| 2| 3| 1| 3| 3| 3| 8| 3| 3| 3| 2| 2| 2| 2| 3| 2| 2| 2| 3| 2| 5| 1|            |
                                           | 0| 6| 0| 9| 1| 5| 0| 0| 9| 5| 0| 1| 0| 9| 9| 9| 9| 0| 9| 9| 9| 0| 9| 8| 0|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|     A      |
    75 PPM                                 | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 0| 5|            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Oviduct                                 |                                                                          |   1        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Leiomyosarcoma                       |                                                                          |          1 |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |             X                                                            |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Vagina                                  |                                                                          |   1        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             | X           X        X                                                   |          3 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |             +  +              +                                         +|   8        |
      Iliac, Lymphoma Malignant Mixed      |                                                                          |          1 |
      Inguinal, Lymphoma Malignant         |                                                                          |            |
          Undifferentiated Cell Type       |                                                                          |          1 |
      Lumbar, Lymphoma Malignant Mixed     |             X                 X                                          |          2 |
      Lumbar, Lymphoma Malignant           |                                                                          |            |
          Undifferentiated Cell Type       |                                                                          |          1 |
      Renal, Lymphoma Malignant Mixed      |             X                                                            |          2 |
      Renal, Lymphoma Malignant            |                                                                          |            |
          Undifferentiated Cell Type       |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  +  +  +  +  +  +  M  M  M  +  +  +  M  M  +  +  M  +  M  +  M  +  M|  32        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |             X                                                            |          2 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  M  +  +|  48        |
      Lymphoma Malignant Mixed             |             X                                         X                  |          4 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +|  49        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |             X                                         X                  |          3 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  33                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 7| 7| 7| 4| 7| 7| 6| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 2|            |
                             DAY ON TEST   | 3| 3| 3| 2| 3| 1| 3| 3| 3| 8| 3| 3| 3| 2| 2| 2| 2| 3| 2| 2| 2| 3| 2| 5| 1|            |
                                           | 0| 6| 0| 9| 1| 5| 0| 0| 9| 5| 0| 1| 0| 9| 9| 9| 9| 0| 9| 9| 9| 0| 9| 8| 0|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|     A      |
    75 PPM                                 | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 0| 5|            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +|  46        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |             X                 X                                          |          4 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             | X           X        X        X                       X                  |          7 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  M  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |             X        X        X                                          |          5 |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Adenocarcinoma                       |                                  X                                       |          1 |
      Adenoma                              |                                     X                                    |          1 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Subcutaneous Tissue, Fibrosarcoma    |                                                                          |          1 |
      Subcutaneous Tissue, Sarcoma         |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                            +                                             |   1        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Adenoma                              |                                                                      X   |          1 |
      Alveolar/Bronchiolar Adenoma         | X                 X                                                      |          5 |
      Alveolar/Bronchiolar Adenoma,        |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  34                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 7| 7| 7| 4| 7| 7| 6| 5| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 5| 2|            |
                             DAY ON TEST   | 3| 3| 3| 2| 3| 1| 3| 3| 3| 8| 3| 3| 3| 2| 2| 2| 2| 3| 2| 2| 2| 3| 2| 5| 1|            |
                                           | 0| 6| 0| 9| 1| 5| 0| 0| 9| 5| 0| 1| 0| 9| 9| 9| 9| 0| 9| 9| 9| 0| 9| 8| 0|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|     A      |
    75 PPM                                 | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 0| 5|            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
          Multiple                         |                                                       X                  |          1 |
      Alveolar/Bronchiolar Carcinoma       |                      X                                                   |          2 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                                                          |          2 |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |             X        X                                                   |          2 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
      Mediastinum, Hepatocellular          |                                                                          |            |
          Carcinoma, Metastatic, Liver     |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                             +        +   |   2        |
      Adenoma                              |                                                             X            |          1 |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |             X        X        X                                          |          3 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |             X                                                            |          3 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
 __________________________________________________________________________________________________________________________________ 
 SYSTEMIC LESIONS                          |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             | X        X  X        X        X                       X                  |          9 |
      Lymphoma Malignant Undifferentiated  |                                                                          |            |
          Cell Type                        |                                                                          |          1 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  35                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 4| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 4| 7| 7| 7| 6|             
                             DAY ON TEST   | 2| 8| 2| 2| 3| 9| 2| 2| 3| 2| 3| 2| 2| 2| 2| 3| 2| 3| 2| 0| 8| 2| 3| 3| 9|             
                                           | 9| 3| 9| 9| 0| 4| 9| 5| 0| 9| 0| 9| 9| 9| 4| 0| 9| 0| 9| 3| 5| 9| 1| 1| 2|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  A  M  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  A  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hepatocellular Carcinoma             |                                              X                 X         |             
      Hepatocellular Adenoma               |                   X                       X                              |             
      Hepatocellular Adenoma, Multiple     |                                                                      X   |             
      Histiocytic Sarcoma                  |                                                             X            |             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
      Lymphoma Malignant Mixed             |                                                       X                  |             
                                            __________________________________________________________________________|             
   Mesentery                               |          +                          +                                    |             
      Lymphoma Malignant Mixed             |          X                                                               |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
      Lymphoma Malignant Mixed             |          X                                                               |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
      Lymphoma Malignant Mixed             |          X                                                               |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |                                                                          |             
      Odontoma                             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcapsular, Lymphoma Malignant Mixed|                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +     +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pheochromocytoma Benign              |                                     X                             X      |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                +              +  +                                       |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  M  +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +  M  M  M  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  +|             
      Pars Distalis, Adenoma               |    X     X              X     X        X     X                    X  X  X|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  36                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 4| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 4| 7| 7| 7| 6|             
                             DAY ON TEST   | 2| 8| 2| 2| 3| 9| 2| 2| 3| 2| 3| 2| 2| 2| 2| 3| 2| 3| 2| 0| 8| 2| 3| 3| 9|             
                                           | 9| 3| 9| 9| 0| 4| 9| 5| 0| 9| 0| 9| 9| 9| 4| 0| 9| 0| 9| 3| 5| 9| 1| 1| 2|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Adenoma             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Clitoral Gland                          |                                  +     +                                 |             
                                            __________________________________________________________________________|             
   Ovary                                   | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cystadenoma                          | X                                                                        |             
      Granulosa Cell Tumor Benign          |                         X                                                |             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                                                                          |             
      Leiomyosarcoma                       |                                                                          |             
      Myxoma                               |                                  X                                       |             
      Polyp Stromal                        |                                                                          |             
                                            __________________________________________________________________________|             
   Vagina                                  |             +                    +                                       |             
      Squamous Cell Carcinoma              |             X                                                            |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
      Lymphoma Malignant Mixed             |                                                                   X      |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                +                          +                             +|             
      Inguinal, Lymphoma Malignant         |                                                                          |             
          Lymphocytic                      |                                                                         X|             
      Inguinal, Lymphoma Malignant Mixed   |                                                                          |             
      Lumbar, Lymphoma Malignant           |                                                                          |             
          Lymphocytic                      |                                                                         X|             
      Lumbar, Lymphoma Malignant Mixed     |                                                                          |             
      Pancreatic, Lymphoma Malignant Mixed |                                                                          |             
      Renal, Lymphoma Malignant Lymphocytic|                                                                         X|             
      Renal, Lymphoma Malignant Mixed      |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  +  +  +  +  +  +  M  +  +  M  +  +  M  M  M  +  M  M  +  +  M  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
      Lymphoma Malignant Mixed             |                                                                   X      |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | M  +  +  +  +  +  +  +  +  +  +  +  M  +  +  M  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                          X              X|             
      Lymphoma Malignant Mixed             |          X                                                               |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|             
      Hemangioma                           |                                                                          |             
      Histiocytic Sarcoma                  |                                                             X            |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  37                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 4| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 4| 7| 7| 7| 6|             
                             DAY ON TEST   | 2| 8| 2| 2| 3| 9| 2| 2| 3| 2| 3| 2| 2| 2| 2| 3| 2| 3| 2| 0| 8| 2| 3| 3| 9|             
                                           | 9| 3| 9| 9| 0| 4| 9| 5| 0| 9| 0| 9| 9| 9| 4| 0| 9| 0| 9| 3| 5| 9| 1| 1| 2|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
      Lymphoma Malignant Mixed             |                                                                   X      |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                          X              X|             
      Lymphoma Malignant Mixed             |          X                                                        X      |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  M  +  M  +  +  +  +  +  M  +  +  +  +  +  +  A  M  +  +  M|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |          X                                            X           X      |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                                          |             
      Sarcoma                              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Peripheral Nerve                        |                                           +                              |             
                                            __________________________________________________________________________|             
   Spinal Cord                             |                                           +                              |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         |             X     X  X  X  X        X        X                 X         |             
      Alveolar/Bronchiolar Adenoma,        |                                                                          |             
          Multiple                         |       X  X                                                               |             
      Alveolar/Bronchiolar Carcinoma       |                                                                      X   |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                X         |             
      Histiocytic Sarcoma                  |                                                             X            |             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
      Lymphoma Malignant Mixed             |                                                                   X      |             
      Mediastinum, Lymphoma Malignant      |                                                                          |             
          Lymphocytic                      |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  38                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 4| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 6| 4| 7| 7| 7| 6|             
                             DAY ON TEST   | 2| 8| 2| 2| 3| 9| 2| 2| 3| 2| 3| 2| 2| 2| 2| 3| 2| 3| 2| 0| 8| 2| 3| 3| 9|             
                                           | 9| 3| 9| 9| 0| 4| 9| 5| 0| 9| 0| 9| 9| 9| 4| 0| 9| 0| 9| 3| 5| 9| 1| 1| 2|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM - cont              |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Ear                                     |                                  +                                       |             
                                            __________________________________________________________________________|             
   Eye                                     |                         +                                                |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                   +                             +                        |             
      Adenoma                              |                   X                             X                        |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                                                             X            |             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
      Lymphoma Malignant Mixed             |                                                       X           X      |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                         X|             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Histiocytic Sarcoma                  |                                                             X            |             
      Lymphoma Malignant Lymphocytic       |                                                          X              X|             
      Lymphoma Malignant Mixed             |          X                                            X           X      |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  39                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 0| 7| 7| 0| 7| 7| 7| 7| 7| 1| 7| 6| 7| 7|            |
                             DAY ON TEST   | 2| 3| 3| 3| 2| 3| 3| 2| 3| 3| 2| 6| 3| 2| 7| 3| 1| 2| 2| 2| 1| 2| 4| 2| 3|            |
                                           | 1| 1| 0| 0| 9| 0| 0| 9| 0| 1| 9| 5| 1| 9| 1| 1| 6| 9| 9| 9| 4| 9| 6| 9| 0|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|     A      |
    150 PPM                                | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | A  +  +  +  +  +  +  +  +  +  +  A  +  +  +  M  A  +  +  +  +  +  A  +  +|  41        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  47        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|  42        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|  45        |
      Lymphoma Malignant Mixed             |                                                                         X|          1 |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|  44        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hepatocellular Carcinoma             |                                              X  X  X                     |          5 |
      Hepatocellular Adenoma               |          X                                         X                     |          4 |
      Hepatocellular Adenoma, Multiple     |                                                                      X   |          2 |
      Histiocytic Sarcoma                  |                                                                          |          1 |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                X                                                        X|          3 |
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   2        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                         X|          2 |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Tooth                                   |                      +                                                   |   1        |
      Odontoma                             |                      X                                                   |          1 |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                             X            |          1 |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Subcapsular, Lymphoma Malignant Mixed|                                                                         X|          1 |
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +     +  +  +  +  +  +  +|  47        |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  40                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 0| 7| 7| 0| 7| 7| 7| 7| 7| 1| 7| 6| 7| 7|            |
                             DAY ON TEST   | 2| 3| 3| 3| 2| 3| 3| 2| 3| 3| 2| 6| 3| 2| 7| 3| 1| 2| 2| 2| 1| 2| 4| 2| 3|            |
                                           | 1| 1| 0| 0| 9| 0| 0| 9| 0| 1| 9| 5| 1| 9| 1| 1| 6| 9| 9| 9| 4| 9| 6| 9| 0|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|     A      |
    150 PPM                                | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 ENDOCRINE SYSTEM - cont                   |                                                                          |            |
                                           |                                                                          |            |
      Pheochromocytoma Benign              |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   3        |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | M  M  M  +  M  M  M  +  +  M  M  M  +  +  +  +  +  +  M  M  +  +  M  +  +|  31        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Pars Distalis, Adenoma               |    X        X  X        X                                                |         13 |
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Follicular Cell, Adenoma             |          X                                                     X         |          2 |
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Clitoral Gland                          |       +                                                                  |   3        |
                                            __________________________________________________________________________|____________|
   Ovary                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Cystadenoma                          |                                                                          |          1 |
      Granulosa Cell Tumor Benign          |                                                                          |          1 |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                         X|          1 |
                                            __________________________________________________________________________|____________|
   Uterus                                  | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Histiocytic Sarcoma                  |          X                                                               |          1 |
      Leiomyosarcoma                       |                X                                                         |          1 |
      Myxoma                               |                                                                          |          1 |
      Polyp Stromal                        |                                                       X                  |          1 |
                                            __________________________________________________________________________|____________|
   Vagina                                  |                                                                          |   2        |
      Squamous Cell Carcinoma              |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                +        +                                               +|   6        |
      Inguinal, Lymphoma Malignant         |                                                                          |            |
          Lymphocytic                      |                                                                          |          1 |
      Inguinal, Lymphoma Malignant Mixed   |                                                                         X|          1 |
      Lumbar, Lymphoma Malignant           |                                                                          |            |
          Lymphocytic                      |                                                                          |          1 |
      Lumbar, Lymphoma Malignant Mixed     |                X                                                         |          1 |
      Pancreatic, Lymphoma Malignant Mixed |                         X                                                |          1 |
      Renal, Lymphoma Malignant Lymphocytic|                                                                          |          1 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  41                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 0| 7| 7| 0| 7| 7| 7| 7| 7| 1| 7| 6| 7| 7|            |
                             DAY ON TEST   | 2| 3| 3| 3| 2| 3| 3| 2| 3| 3| 2| 6| 3| 2| 7| 3| 1| 2| 2| 2| 1| 2| 4| 2| 3|            |
                                           | 1| 1| 0| 0| 9| 0| 0| 9| 0| 1| 9| 5| 1| 9| 1| 1| 6| 9| 9| 9| 4| 9| 6| 9| 0|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|     A      |
    150 PPM                                | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
      Renal, Lymphoma Malignant Mixed      |                                                                         X|          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | M  +  +  +  M  +  +  M  +  M  +  +  +  M  +  M  +  M  +  +  +  M  M  M  M|  30        |
      Lymphoma Malignant Lymphocytic       |                                                             X            |          2 |
      Lymphoma Malignant Mixed             |                         X                                                |          2 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  M|  45        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          2 |
      Lymphoma Malignant Mixed             |                         X                                                |          2 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  A  +  +|  45        |
      Hemangioma                           |                                                 X                        |          1 |
      Histiocytic Sarcoma                  |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                         X|          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | M  +  +  +  +  +  +  +  +  +  +  M  M  +  +  +  +  M  +  M  +  +  +  +  +|  43        |
      Lymphoma Malignant Lymphocytic       |                                                             X            |          2 |
      Lymphoma Malignant Mixed             |                         X                                               X|          3 |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          2 |
      Lymphoma Malignant Mixed             |                X        X                                               X|          5 |
                                            __________________________________________________________________________|____________|
   Thymus                                  | M  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  41        |
      Lymphoma Malignant Lymphocytic       |                                                             X            |          1 |
      Lymphoma Malignant Mixed             |                X        X                                               X|          6 |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                                                    +                     |   1        |
      Sarcoma                              |                                                    X                     |          1 |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Peripheral Nerve                        |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Spinal Cord                             |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  42                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 0| 7| 7| 0| 7| 7| 7| 7| 7| 1| 7| 6| 7| 7|            |
                             DAY ON TEST   | 2| 3| 3| 3| 2| 3| 3| 2| 3| 3| 2| 6| 3| 2| 7| 3| 1| 2| 2| 2| 1| 2| 4| 2| 3|            |
                                           | 1| 1| 0| 0| 9| 0| 0| 9| 0| 1| 9| 5| 1| 9| 1| 1| 6| 9| 9| 9| 4| 9| 6| 9| 0|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE FEMALE                      | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|     A      |
    150 PPM                                | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
      Alveolar/Bronchiolar Adenoma         |                         X  X                       X  X        X  X  X   |         15 |
      Alveolar/Bronchiolar Adenoma,        |                                                                          |            |
          Multiple                         |                                                                          |          2 |
      Alveolar/Bronchiolar Carcinoma       |                   X                                                      |          2 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                              X  X                        |          3 |
      Histiocytic Sarcoma                  |                                                                          |          1 |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
      Mediastinum, Lymphoma Malignant      |                                                                          |            |
          Lymphocytic                      |                                                             X            |          1 |
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Ear                                     |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   2        |
      Adenoma                              |                                                                          |          2 |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Histiocytic Sarcoma                  |                                                                          |          1 |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          2 |
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  47        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
 __________________________________________________________________________________________________________________________________ 
 SYSTEMIC LESIONS                          |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Histiocytic Sarcoma                  |          X                                                               |          2 |
      Lymphoma Malignant Lymphocytic       |                                                             X            |          3 |
      Lymphoma Malignant Mixed             |                X        X                                               X|          6 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  43                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 7| 4| 7| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 1| 2| 2| 2| 2| 5| 2| 2| 2| 2| 2| 2| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
                                           | 6| 2| 6| 5| 5| 5| 5| 6| 9| 6| 5| 6| 5| 8| 6| 5| 5| 6| 6| 6| 6| 5| 6| 6| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  A  +  A  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  A  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  A  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  A  +  M  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangiosarcoma                      |                                                       X                  |             
      Hemangiosarcoma, Multiple            |                                                                          |             
      Hepatocellular Carcinoma             |    X     X        X     X  X                       X                     |             
      Hepatocellular Carcinoma, Multiple   |                X                                                         |             
      Hepatocellular Adenoma               | X                 X                                      X  X  X         |             
      Hepatocellular Adenoma, Multiple     |                                           X                             X|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |             +                                                            |             
      Odontoma                             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                       +              +  +|             
      Adenoma                              |                                                                         X|             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  +  +  +  +  +  +  +  +  M  M  M  M  M  M  M  M  +  M  +  +  +  M  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Follicular Cell, Adenoma             |                X                                                         |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  44                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 7| 4| 7| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 1| 2| 2| 2| 2| 5| 2| 2| 2| 2| 2| 2| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
                                           | 6| 2| 6| 5| 5| 5| 5| 6| 9| 6| 5| 6| 5| 8| 6| 5| 5| 6| 6| 6| 6| 5| 6| 6| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Penis                                   |    +                                                                     |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +        +                 +  +  +     +        +     +  +        +  +   |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                        +                                 |             
      Lumbar, Lymphoma Malignant Mixed     |                                        X                                 |             
      Renal, Lymphoma Malignant Mixed      |                                        X                                 |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  M  M  +  M  +  +  +  +  M  +  M     M  M  M  +  M  +  M  M  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  M  +  +  M  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  M|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  M  M  M  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  M  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangioma                           |                                                                          |             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  M  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  +  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcutaneous Tissue, Lymphoma        |                                                                          |             
          Malignant Mixed                  |                                        X                                 |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         |          X                          X           X        X               |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  45                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 5| 7| 7| 7| 7| 4| 7| 5| 7| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 1| 2| 2| 2| 2| 5| 2| 2| 2| 2| 2| 2| 1| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
                                           | 6| 2| 6| 5| 5| 5| 5| 6| 9| 6| 5| 6| 5| 8| 6| 5| 5| 6| 6| 6| 6| 5| 6| 6| 9|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
    CONTROL                                | 0| 0| 0| 0| 0| 0| 0| 0| 0| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 2| 2| 2| 2| 2| 2|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
      Alveolar/Bronchiolar Carcinoma       |                                                                          |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |          X     X                                   X                     |             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                      +                       +        +                 +|             
      Adenoma                              |                                              X        X                 X|             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                        X                                 |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  46                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 0| 7| 7| 7| 7| 7| 7| 7| 7| 5| 1| 6| 7| 7| 7| 7| 5| 5| 5| 7| 4| 7|            |
                             DAY ON TEST   | 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 0| 3| 0| 2| 2| 1| 2| 6| 7| 9| 2| 7| 2|            |
                                           | 6| 6| 6| 1| 6| 6| 6| 6| 6| 6| 6| 5| 9| 6| 4| 5| 6| 1| 5| 3| 0| 4| 6| 9| 5|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     A      |
    CONTROL                                | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  +  +  M  +  A  +  +  A  +  A  A  A  +  +  +|  41        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  A  +  A  A  +  +  +  +|  44        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  A  +  +  A  A  +  A  +|  43        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  A  A  A  +  A  +|  42        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  A  A  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hemangiosarcoma                      |                                                                          |          1 |
      Hemangiosarcoma, Multiple            |                                           X                              |          1 |
      Hepatocellular Carcinoma             |                               X     X                                X   |          9 |
      Hepatocellular Carcinoma, Multiple   |                                                          X     X         |          3 |
      Hepatocellular Adenoma               |             X     X                                X        X           X|         10 |
      Hepatocellular Adenoma, Multiple     |                               X                                   X      |          4 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Tooth                                   |       +                                                     +            |   3        |
      Odontoma                             |       X                                                                  |          1 |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |             +  +                                                         |   5        |
      Adenoma                              |             X                                                            |          2 |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | M  +  +  +  M  +  M  +  +  M  M  +  +  +  M  +  +  +  M  +  +  +  M  +  M|  29        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +|  47        |
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Follicular Cell, Adenoma             |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  47                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 0| 7| 7| 7| 7| 7| 7| 7| 7| 5| 1| 6| 7| 7| 7| 7| 5| 5| 5| 7| 4| 7|            |
                             DAY ON TEST   | 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 0| 3| 0| 2| 2| 1| 2| 6| 7| 9| 2| 7| 2|            |
                                           | 6| 6| 6| 1| 6| 6| 6| 6| 6| 6| 6| 5| 9| 6| 4| 5| 6| 1| 5| 3| 0| 4| 6| 9| 5|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     A      |
    CONTROL                                | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Penis                                   |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Preputial Gland                         |       +                 +     +              +                          +|  16        |
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   1        |
      Lumbar, Lymphoma Malignant Mixed     |                                                                          |          1 |
      Renal, Lymphoma Malignant Mixed      |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  M  +  M  M  M  +  M  +  M  M  +  +  +  M  M  +  M  +  +  M  +  M  +  M|  25        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  M  +  +  M  +  M  +  +  +  +  +  +  +  +  +  M  +  +  M  +  M  M  +  +|  39        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  A  +  A  +  +  +  +  +|  47        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  M  M  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +|  41        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hemangioma                           |                                  X                                       |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +|  45        |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  +  M  M  M  M  M  M  +  M  M  M|   3        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Subcutaneous Tissue, Lymphoma        |                                                                          |            |
          Malignant Mixed                  |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  48                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 0| 7| 7| 7| 7| 7| 7| 7| 7| 5| 1| 6| 7| 7| 7| 7| 5| 5| 5| 7| 4| 7|            |
                             DAY ON TEST   | 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 0| 3| 0| 2| 2| 1| 2| 6| 7| 9| 2| 7| 2|            |
                                           | 6| 6| 6| 1| 6| 6| 6| 6| 6| 6| 6| 5| 9| 6| 4| 5| 6| 1| 5| 3| 0| 4| 6| 9| 5|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     A      |
    CONTROL                                | 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 5|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 NERVOUS SYSTEM - cont                     |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Alveolar/Bronchiolar Adenoma         |                                           X     X                 X      |          7 |
      Alveolar/Bronchiolar Carcinoma       |                   X                                                      |          1 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                     X                    X               |          5 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                    +                     |   5        |
      Adenoma                              |                                                    X                     |          4 |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 __________________________________________________________________________________________________________________________________ 
 SYSTEMIC LESIONS                          |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  49                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 5| 7| 7| 7| 7| 1| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 5| 7| 7| 3| 6|             
                             DAY ON TEST   | 2| 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 6| 9| 2| 8| 2| 2| 7| 1|             
                                           | 5| 6| 5| 5| 1| 5| 9| 9| 5| 4| 4| 5| 5| 5| 5| 9| 5| 7| 2| 6| 1| 5| 6| 9| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  M  +  A  +  +  +  +  +  +  +  M  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
      Hemangiosarcoma                      |                               X                                          |             
      Hemangiosarcoma, Multiple            |                                     X                                    |             
      Hepatocellular Carcinoma             |                                                       X                  |             
      Hepatocellular Carcinoma, Multiple   |       X                                                                  |             
      Hepatocellular Adenoma               | X        X           X              X        X     X              X      |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                                                   +      |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                             X            |             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcapsular, Adenoma                 | X                                                                        |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pheochromocytoma Benign              |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                              +                           |             
      Adenoma                              |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | M  +  +  +  +  M  +  M  M  +  M  +  +  +  +  M  +  +  +  +  M  M  M  M  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | M  +  +  +  +  M  +  +  +  M  +  +  +  +  +  I  +  +  +  +  +  +  +  +  +|             
      Pars Intermedia, Adenoma             |                                                                          |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
      Follicular Cell, Carcinoma           |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  50                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 5| 7| 7| 7| 7| 1| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 5| 7| 7| 3| 6|             
                             DAY ON TEST   | 2| 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 6| 9| 2| 8| 2| 2| 7| 1|             
                                           | 5| 6| 5| 5| 1| 5| 9| 9| 5| 4| 4| 5| 5| 5| 5| 9| 5| 7| 2| 6| 1| 5| 6| 9| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                             X            |             
                                            __________________________________________________________________________|             
   Penis                                   |                                                                         +|             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +  +  +  +     +                 +     +              +  +  +         |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangiosarcoma                      |       X                                                                  |             
                                            __________________________________________________________________________|             
   Lymph Node                              |             +                                                        +   |             
      Lymphoma Malignant Mixed             |                                                                          |             
      Inguinal, Alveolar/Bronchiolar       |                                                                          |             
          Carcinoma, Metastatic, Lung      |                                                                          |             
      Renal, Lymphoma Malignant Mixed      |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  M  M  +  +  +  +  +  +  +  M  +  +  +  M  M  +  M  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                             X            |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | M  +  +  M  +  +  +  +  +  +  +  +  +  M  +     +  +  +  +  +  M  +  M  +|             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                       X                  |             
      Lymphoma Malignant Mixed             |                                                             X            |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                             X            |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  +  M  M  M  M  M  M  M  M  M  M  M  M  A  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  51                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 7| 5| 7| 7| 7| 7| 1| 7| 7| 7| 7| 7| 7| 7| 6| 6| 7| 5| 7| 7| 3| 6|             
                             DAY ON TEST   | 2| 2| 2| 2| 6| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 6| 9| 2| 8| 2| 2| 7| 1|             
                                           | 5| 6| 5| 5| 1| 5| 9| 9| 5| 4| 4| 5| 5| 5| 5| 9| 5| 7| 2| 6| 1| 5| 6| 9| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|             
    37.5 PPM                               | 2| 2| 2| 2| 2| 2| 2| 2| 2| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM - cont             |                                                                          |             
                                           |                                                                          |             
      Mandible, Alveolar/Bronchiolar       |                                                                          |             
          Carcinoma, Metastatic, Lung      |                                                                          |             
      Rib, Alveolar/Bronchiolar Carcinoma, |                                                                          |             
           Metastatic, Lung                |                                                                          |             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                                                                          |             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Spinal Cord                             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         | X  X                    X                                      X         |             
      Alveolar/Bronchiolar Adenoma,        |                                                                          |             
          Multiple                         |                      X                                                   |             
      Alveolar/Bronchiolar Carcinoma       |          X        X                                                      |             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Multiple                         |                                                    X                     |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |       X                                               X                  |             
      Lymphoma Malignant Mixed             |                                                             X            |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                              +                           |             
      Adenoma                              |                                              X                           |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
      Renal Tubule, Adenoma                |                               X                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                             X            |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  52                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 6| 7| 7| 7| 6| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 6| 7| 7|            |
                             DAY ON TEST   | 2| 9| 6| 2| 2| 2| 9| 2| 2| 2| 0| 8| 2| 2| 2| 8| 2| 2| 2| 2| 2| 2| 8| 2| 2|            |
                                           | 6| 9| 7| 5| 5| 6| 3| 6| 6| 6| 3| 4| 6| 6| 6| 2| 6| 5| 5| 6| 6| 6| 7| 5| 5|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|     A      |
    37.5 PPM                               | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  M  M  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|  46        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  +  A  +  +  M  A  A  +  +  +  A  +  +  +  +  +  +  +  +  +|  40        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  A  +  +  +  A  A  +  +  +  +  +  +  +  +  +  M  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  A  +  +  +  A  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  45        |
      Lymphoma Malignant Mixed             |                                                    X                     |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|  45        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 |                   X                                                      |          1 |
      Hemangiosarcoma                      |                                                                          |          1 |
      Hemangiosarcoma, Multiple            |                                                                          |          1 |
      Hepatocellular Carcinoma             |       X                          X           X                          X|          5 |
      Hepatocellular Carcinoma, Multiple   |                                                                          |          1 |
      Hepatocellular Adenoma               |       X                 X     X  X  X     X              X           X   |         15 |
      Lymphoma Malignant Mixed             |                                                    X                     |          1 |
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 |                   X                                                      |          1 |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Subcapsular, Adenoma                 |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
      Pheochromocytoma Benign              |          X                          X                                    |          2 |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                +         |   2        |
      Adenoma                              |                                                                X         |          1 |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  M  M  M  M  M  +  +  +  +  +  +  +  +  +  M  +  +  +  M  +  +  M  +  M|  31        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  46        |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  53                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 6| 7| 7| 7| 6| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 6| 7| 7|            |
                             DAY ON TEST   | 2| 9| 6| 2| 2| 2| 9| 2| 2| 2| 0| 8| 2| 2| 2| 8| 2| 2| 2| 2| 2| 2| 8| 2| 2|            |
                                           | 6| 9| 7| 5| 5| 6| 3| 6| 6| 6| 3| 4| 6| 6| 6| 2| 6| 5| 5| 6| 6| 6| 7| 5| 5|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|     A      |
    37.5 PPM                               | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 ENDOCRINE SYSTEM - cont                   |                                                                          |            |
                                           |                                                                          |            |
      Pars Intermedia, Adenoma             |                                                                         X|          1 |
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 |                   X                                                      |          1 |
      Follicular Cell, Carcinoma           |             X                                                            |          1 |
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Penis                                   |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Preputial Gland                         |             +     +  +        +  +  +                    +        +      |  19        |
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Hemangiosarcoma                      |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                   +                                +     +               |   5        |
      Lymphoma Malignant Mixed             |                                                          X               |          1 |
      Inguinal, Alveolar/Bronchiolar       |                                                                          |            |
          Carcinoma, Metastatic, Lung      |                   X                                                      |          1 |
      Renal, Lymphoma Malignant Mixed      |                                                    X     X               |          2 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  M  +  +  M  +  M  +  +  +  +  M  +  +  M  +  +  +  +  M  +  +  M  M  +|  36        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 |                   X                                                      |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
      Lymphoma Malignant Mixed             |                                                    X     X               |          3 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  M  +  +  +  +  +  M  M  +  +  +  +  +  +  +  M  M  +  +  M  M  +|  37        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 |                   X                                                      |          1 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                    X                     |          2 |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  54                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 6| 7| 7| 7| 6| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 6| 7| 7|            |
                             DAY ON TEST   | 2| 9| 6| 2| 2| 2| 9| 2| 2| 2| 0| 8| 2| 2| 2| 8| 2| 2| 2| 2| 2| 2| 8| 2| 2|            |
                                           | 6| 9| 7| 5| 5| 6| 3| 6| 6| 6| 3| 4| 6| 6| 6| 2| 6| 5| 5| 6| 6| 6| 7| 5| 5|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|     A      |
    37.5 PPM                               | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
      Lymphoma Malignant Mixed             |                                                    X     X               |          3 |
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  M  +  +  +|  46        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 |                   X                                                      |          1 |
      Lymphoma Malignant Mixed             |                                                    X                     |          1 |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M|   1        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Mandible, Alveolar/Bronchiolar       |                                                                          |            |
          Carcinoma, Metastatic, Lung      |                   X                                                      |          1 |
      Rib, Alveolar/Bronchiolar Carcinoma, |                                                                          |            |
           Metastatic, Lung                |                   X                                                      |          1 |
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                   +                                                      |   1        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 |                   X                                                      |          1 |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Spinal Cord                             |    +                                                                     |   1        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Alveolar/Bronchiolar Adenoma         | X                                      X        X  X  X                  |          9 |
      Alveolar/Bronchiolar Adenoma,        |                                                                          |            |
          Multiple                         |                            X                                         X   |          3 |
      Alveolar/Bronchiolar Carcinoma       |                   X                             X                    X   |          5 |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Multiple                         |                                                                          |          1 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |       X                          X           X                          X|          6 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  55                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 6| 6| 7| 7| 7| 6| 7| 7| 7| 7| 6| 7| 7| 7| 6| 7| 7| 7| 7| 7| 7| 6| 7| 7|            |
                             DAY ON TEST   | 2| 9| 6| 2| 2| 2| 9| 2| 2| 2| 0| 8| 2| 2| 2| 8| 2| 2| 2| 2| 2| 2| 8| 2| 2|            |
                                           | 6| 9| 7| 5| 5| 6| 3| 6| 6| 6| 3| 4| 6| 6| 6| 2| 6| 5| 5| 6| 6| 6| 7| 5| 5|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1| 1|     A      |
    37.5 PPM                               | 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6| 6| 6| 6| 6| 7|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 SPECIAL SENSES SYSTEM - cont              |                                                                          |            |
                                           |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   1        |
      Adenoma                              |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 |                   X                                                      |          1 |
      Renal Tubule, Adenoma                |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  48        |
 __________________________________________________________________________________________________________________________________ 
 SYSTEMIC LESIONS                          |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Mixed             |                                                    X     X               |          3 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  56                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 6| 7| 5| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 5| 6| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 1| 2| 5| 2| 2| 2| 0| 2| 2| 2| 2| 2| 2| 5| 6| 5| 2| 2| 2| 2|             
                                           | 6| 6| 6| 4| 6| 4| 6| 7| 6| 6| 6| 8| 5| 6| 9| 6| 5| 6| 8| 2| 8| 5| 5| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cholangiocarcinoma                   |                                                          X               |             
      Hemangiosarcoma                      |                                           X                              |             
      Hepatocellular Carcinoma             |                      X     X                             X  X            |             
      Hepatocellular Carcinoma, Multiple   |                                                                          |             
      Hepatocellular Adenoma               |          X        X                       X  X           X  X           X|             
      Hepatocellular Adenoma, Multiple     |                                                                X         |             
                                            __________________________________________________________________________|             
   Mesentery                               |    +                             +                       +               |             
      Cholangiocarcinoma, Metastatic, Liver|                                                          X               |             
      Hemangiosarcoma                      |    X                                                                     |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Tooth                                   |                               +                                          |             
      Odontoma                             |                               X                                          |             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Metastatic, Lung                 |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                               +                       +                  |             
      Adenoma                              |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  M  M  M  +  +  M  +  M  +  +  +  +  +  +  +  +  +  +  M  +  +  M  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  M  +  +  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
      Pars Distalis, Adenoma               |                                           X                              |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      C-Cell, Carcinoma                    |                                                       X                  |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  57                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 6| 7| 5| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 5| 6| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 1| 2| 5| 2| 2| 2| 0| 2| 2| 2| 2| 2| 2| 5| 6| 5| 2| 2| 2| 2|             
                                           | 6| 6| 6| 4| 6| 4| 6| 7| 6| 6| 6| 8| 5| 6| 9| 6| 5| 6| 8| 2| 8| 5| 5| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM - cont                   |                                                                          |             
                                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Tissue NOS                              |                                  +                                       |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cholangiocarcinoma, Metastatic, Liver|                                                          X               |             
                                            __________________________________________________________________________|             
   Penis                                   |          +                                                               |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +                       +     +        +        +  +              +      |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Interstitial Cell, Adenoma           |    X                                                                     |             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Blood                                   |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                                  +                       +              +|             
      Inguinal, Cholangiocarcinoma,        |                                                                          |             
          Metastatic, Liver                |                                                          X               |             
      Inguinal, Lymphoma Malignant         |                                                                          |             
          Lymphocytic                      |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | M  M  M  M  M  M  +  +  M  M  M  +  +  +  M  M  M  M  M  M  +  M  M  M  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +|             
      Cholangiocarcinoma, Metastatic, Liver|                                                          X               |             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  M  +  +  M  +  +  +  M  +  M  +  M  M  +  +  +  +  +  +  +  +  +  M|             
      Cholangiocarcinoma, Metastatic, Liver|                                                          X               |             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangiosarcoma                      |    X                                                                     |             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  M  +  +  +  M  +  M  +  +  +  +  +  +  +  +  +  M  +  M  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  58                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 6| 7| 5| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 5| 6| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 1| 2| 5| 2| 2| 2| 0| 2| 2| 2| 2| 2| 2| 5| 6| 5| 2| 2| 2| 2|             
                                           | 6| 6| 6| 4| 6| 4| 6| 7| 6| 6| 6| 8| 5| 6| 9| 6| 5| 6| 8| 2| 8| 5| 5| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM - cont               |                                                                          |             
                                           |                                                                          |             
      Subcutaneous Tissue,                 |                                                                          |             
          Alveolar/Bronchiolar Carcinoma,  |                                                                          |             
           Metastatic, Lung                |                                                                          |             
      Subcutaneous Tissue, Schwannoma      |                                                                          |             
          Malignant, Multiple              |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Skeletal Muscle                         |                   +                                                      |             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         |                   X        X        X  X     X  X                    X  X|             
      Alveolar/Bronchiolar Adenoma,        |                                                                          |             
          Multiple                         | X                                                  X                     |             
      Alveolar/Bronchiolar Carcinoma       |                                                                      X   |             
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |             
          Multiple                         |                                                                          |             
      Cholangiocarcinoma, Metastatic, Liver|                                                          X               |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                      X                                                   |             
      Mediastinum, Cholangiocarcinoma,     |                                                                          |             
           Metastatic, Liver               |                                                          X               |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                      +   |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                                                                   +  +   |             
      Adenoma                              |                                                                   X  X   |             
                                            __________________________________________________________________________|             
   Zymbal's Gland                          | +                                                                        |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cholangiocarcinoma, Metastatic, Liver|                                                          X               |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                          |             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Cholangiocarcinoma, Metastatic, Liver|                                                          X               |             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  59                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 6| 7| 5| 7| 7| 7| 4| 7| 7| 7| 7| 7| 7| 5| 6| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 6| 2| 1| 2| 5| 2| 2| 2| 0| 2| 2| 2| 2| 2| 2| 5| 6| 5| 2| 2| 2| 2|             
                                           | 6| 6| 6| 4| 6| 4| 6| 7| 6| 6| 6| 8| 5| 6| 9| 6| 5| 6| 8| 2| 8| 5| 5| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|             
    75 PPM                                 | 4| 4| 4| 4| 4| 4| 4| 4| 4| 5| 5| 5| 5| 5| 5| 5| 5| 5| 5| 6| 6| 6| 6| 6| 6|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS - cont                   |                                                                          |             
                                           |                                                                          |             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  60                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 5| 7| 4| 7| 7| 7| 3| 7| 7| 6| 7| 6| 6|            |
                             DAY ON TEST   | 2| 2| 0| 2| 2| 2| 2| 2| 8| 2| 2| 2| 7| 2| 8| 2| 2| 2| 0| 2| 2| 8| 2| 4| 1|            |
                                           | 5| 5| 1| 9| 5| 5| 6| 6| 3| 6| 6| 5| 9| 6| 4| 5| 6| 5| 7| 6| 6| 1| 5| 7| 9|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|     A      |
    75 PPM                                 | 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 9|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +  +  +  M  +  +  A  M  +  +  +  +  A  +  +  M  +  +  +  +  +  +  +|  42        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  A|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A|  48        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  A  +  A  +  +  +  +  +  +  +  +  +  A|  45        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  A  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A|  46        |
      Lymphoma Malignant Mixed             |                                              X                           |          1 |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  A|  45        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cholangiocarcinoma                   |                                                                          |          1 |
      Hemangiosarcoma                      |                                                                          |          1 |
      Hepatocellular Carcinoma             |       X           X                 X     X                          X   |          9 |
      Hepatocellular Carcinoma, Multiple   |                                                    X                    X|          2 |
      Hepatocellular Adenoma               |                   X        X        X        X                    X  X   |         13 |
      Hepatocellular Adenoma, Multiple     |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Mesentery                               |             +                          +                                 |   5        |
      Cholangiocarcinoma, Metastatic, Liver|                                                                          |          1 |
      Hemangiosarcoma                      |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                      X                                                   |          1 |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  +     +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  +     +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Tooth                                   |                                                                          |   1        |
      Odontoma                             |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +     +|  48        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 | X                                                                        |          1 |
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +     +|  48        |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Metastatic, Lung                 | X                                                                        |          1 |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |             +              +  +  +                       +     +  +      |   9        |
      Adenoma                              |                                  X                             X         |          2 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  61                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 5| 7| 4| 7| 7| 7| 3| 7| 7| 6| 7| 6| 6|            |
                             DAY ON TEST   | 2| 2| 0| 2| 2| 2| 2| 2| 8| 2| 2| 2| 7| 2| 8| 2| 2| 2| 0| 2| 2| 8| 2| 4| 1|            |
                                           | 5| 5| 1| 9| 5| 5| 6| 6| 3| 6| 6| 5| 9| 6| 4| 5| 6| 5| 7| 6| 6| 1| 5| 7| 9|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|     A      |
    75 PPM                                 | 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 9|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 ENDOCRINE SYSTEM - cont                   |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  M  M  +  M  M  M  +  M  +|  35        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +|  46        |
      Pars Distalis, Adenoma               |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      C-Cell, Carcinoma                    |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Tissue NOS                              |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cholangiocarcinoma, Metastatic, Liver|                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Penis                                   |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Preputial Gland                         | +        +                 +     +     +                          +     +|  14        |
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Interstitial Cell, Adenoma           |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Blood                                   |                                     +                                    |   1        |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                      +                                   +               |   5        |
      Inguinal, Cholangiocarcinoma,        |                                                                          |            |
          Metastatic, Liver                |                                                                          |          1 |
      Inguinal, Lymphoma Malignant         |                                                                          |            |
          Lymphocytic                      |                      X                                                   |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | M  +  M  M  M  +  M  +  +  M  M  +  M  +  +  +  M  M  +  M  +  M  +  M  M|  18        |
      Lymphoma Malignant Lymphocytic       |                      X                                                   |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                      X                                                   |          1 |
      Lymphoma Malignant Mixed             |                                              X                           |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  47        |
      Cholangiocarcinoma, Metastatic, Liver|                                                                          |          1 |
      Lymphoma Malignant Lymphocytic       |                      X                                                   |          1 |
      Lymphoma Malignant Mixed             |                                              X                           |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +  +  +  +  +  +  +  M  +  +  M  +  A  M  +  +  +  +  +  +  +  +  +|  39        |
      Cholangiocarcinoma, Metastatic, Liver|                                                                          |          1 |
      Lymphoma Malignant Lymphocytic       |                      X                                                   |          1 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  62                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 5| 7| 4| 7| 7| 7| 3| 7| 7| 6| 7| 6| 6|            |
                             DAY ON TEST   | 2| 2| 0| 2| 2| 2| 2| 2| 8| 2| 2| 2| 7| 2| 8| 2| 2| 2| 0| 2| 2| 8| 2| 4| 1|            |
                                           | 5| 5| 1| 9| 5| 5| 6| 6| 3| 6| 6| 5| 9| 6| 4| 5| 6| 5| 7| 6| 6| 1| 5| 7| 9|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|     A      |
    75 PPM                                 | 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 9|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 HEMATOPOIETIC SYSTEM - cont               |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
      Hemangiosarcoma                      |                                                                          |          1 |
      Lymphoma Malignant Lymphocytic       |                      X                                                   |          1 |
      Lymphoma Malignant Mixed             |                                              X                           |          1 |
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  +  +  M  +  M  +  +  +  +  +  +  M  A  +  +  +  M  M  M  +  +  +  +|  38        |
      Lymphoma Malignant Lymphocytic       |                      X                                                   |          1 |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  +  M  M  M  M  M  M|   1        |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
      Subcutaneous Tissue,                 |                                                                          |            |
          Alveolar/Bronchiolar Carcinoma,  |                                                                          |            |
           Metastatic, Lung                | X                                                                        |          1 |
      Subcutaneous Tissue, Schwannoma      |                                                                          |            |
          Malignant, Multiple              |                X                                                         |          1 |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Skeletal Muscle                         |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  49        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +|  49        |
      Alveolar/Bronchiolar Adenoma         |             X                          X                                 |         10 |
      Alveolar/Bronchiolar Adenoma,        |                                                                          |            |
          Multiple                         |                      X                                                   |          3 |
      Alveolar/Bronchiolar Carcinoma       | X                             X        X                                 |          4 |
      Alveolar/Bronchiolar Carcinoma,      |                                                                          |            |
          Multiple                         |                                                    X                     |          1 |
      Cholangiocarcinoma, Metastatic, Liver|                                                                          |          1 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                   X                                X                    X|          4 |
      Mediastinum, Cholangiocarcinoma,     |                                                                          |            |
           Metastatic, Liver               |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  63                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 7| 7| 7| 7| 7| 7| 7| 7| 5| 7| 7| 7| 5| 7| 4| 7| 7| 7| 3| 7| 7| 6| 7| 6| 6|            |
                             DAY ON TEST   | 2| 2| 0| 2| 2| 2| 2| 2| 8| 2| 2| 2| 7| 2| 8| 2| 2| 2| 0| 2| 2| 8| 2| 4| 1|            |
                                           | 5| 5| 1| 9| 5| 5| 6| 6| 3| 6| 6| 5| 9| 6| 4| 5| 6| 5| 7| 6| 6| 1| 5| 7| 9|            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|     T      |
                               ANIMAL ID   | 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2| 2|     A      |
    75 PPM                                 | 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8| 8| 8| 8| 8| 9|     L      |
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                            +                                             |   3        |
      Adenoma                              |                            X                                             |          3 |
                                            __________________________________________________________________________|____________|
   Zymbal's Gland                          |                                                                          |   1        |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Cholangiocarcinoma, Metastatic, Liver|                                                                          |          1 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                   X                                                      |          1 |
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +|  49        |
      Cholangiocarcinoma, Metastatic, Liver|                                                                          |          1 |
 __________________________________________________________________________________________________________________________________ 
 SYSTEMIC LESIONS                          |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|  50        |
      Lymphoma Malignant Lymphocytic       |                      X                                                   |          1 |
      Lymphoma Malignant Mixed             |                                              X                           |          1 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  64                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 7| 7| 5| 7| 4| 7| 5| 6| 7| 7| 7| 5| 7| 5| 2| 7| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 4| 2| 2| 7| 2| 4| 2| 5| 6| 2| 2| 2| 5| 2| 4| 3| 2| 8| 2| 2| 2| 2|             
                                           | 5| 5| 6| 0| 5| 6| 5| 5| 3| 5| 3| 8| 5| 5| 5| 8| 6| 1| 5| 4| 8| 6| 9| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    150 PPM                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  A  +  +  +  +  A  +  +  +  +  +  A  A  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | A  +  +  A  +  +  +  +  A  +  +  A  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | A  +  +  +  +  +  +  +  A  +  +  A  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  A  +  +  A  +  A  +  +  A  +  +  M  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | A  +  +  A  +  +  +  +  A  +  +  A  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangiosarcoma                      |                   X           X                                          |             
      Hemangiosarcoma, Multiple            |                                                                          |             
      Hepatocellular Carcinoma             |          X                 X     X           X              X           X|             
      Hepatocellular Adenoma               |          X                 X     X  X     X        X     X  X           X|             
      Hepatocellular Adenoma, Multiple     |                                                                          |             
                                            __________________________________________________________________________|             
   Mesentery                               |                               +                       +                  |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
      Squamous Cell Carcinoma              |                                  X                                       |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  A  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
      Subcapsular, Adenoma                 |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  A  +  +  +  +  M  +  +  +  +  +  +  +  +  +  +  +|             
      Pheochromocytoma Benign              |                                                                          |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                                          |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  M  +  M  +  +  +  +  +  +  +  M  +  M  M  +  +  +  +  +  +  +  +  +  M|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  M  M  +  +  +  +  M  +  +  +  +  +  +  M|             
      Pars Distalis, Adenoma               |                                                                          |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Bilateral, Follicular Cell, Adenoma  |                                                                          |             
      Follicular Cell, Adenoma             |                                                                      X   |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Coagulating Gland                       |                                                    A                     |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Penis                                   |          +                             +                                 |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  65                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 7| 7| 5| 7| 4| 7| 5| 6| 7| 7| 7| 5| 7| 5| 2| 7| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 4| 2| 2| 7| 2| 4| 2| 5| 6| 2| 2| 2| 5| 2| 4| 3| 2| 8| 2| 2| 2| 2|             
                                           | 5| 5| 6| 0| 5| 6| 5| 5| 3| 5| 3| 8| 5| 5| 5| 8| 6| 1| 5| 4| 8| 6| 9| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    150 PPM                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +              +  +  +                                            +     +|             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              | +                       +                                                |             
      Inguinal, Lymphoma Malignant Mixed   | X                                                                        |             
      Lumbar, Lymphoma Malignant Mixed     | X                                                                        |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  +  +  +  M  M  M  +  +  +  +  M  +  M  +  +  M  +  +  M  M  +  +  +  M|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  +  +  +  +  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  M  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                      X   |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  A  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                      X   |             
      Lymphoma Malignant Mixed             | X                                                                        |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | +  +  +  +  +  M  +  M  M  +  +  +  M  +  M  +  +  +  +  +  M  M  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                      X   |             
      Lymphoma Malignant Mixed             | X                                                                        |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
      Sarcoma, Metastatic, Skin            |                                                                          |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  M  +  A  +  M  +  +  +  +  M|             
      Lymphoma Malignant Mixed             | X                                                                        |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +|             
      Subcutaneous Tissue, Sarcoma         |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  M  +  +  +  M  +  I  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         | X     X                                         X           X        X   |             
      Alveolar/Bronchiolar Adenoma,        |                                                                          |             
          Multiple                         |             X                                                           X|             
      Alveolar/Bronchiolar Carcinoma       |                                              X                           |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                         X|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  66                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 6| 7| 7| 6| 7| 7| 5| 7| 4| 7| 5| 6| 7| 7| 7| 5| 7| 5| 2| 7| 5| 7| 7| 7| 7|             
                             DAY ON TEST   | 2| 2| 2| 4| 2| 2| 7| 2| 4| 2| 5| 6| 2| 2| 2| 5| 2| 4| 3| 2| 8| 2| 2| 2| 2|             
                                           | 5| 5| 6| 0| 5| 6| 5| 5| 3| 5| 3| 8| 5| 5| 5| 8| 6| 1| 5| 4| 8| 6| 9| 6| 6|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3|             
    150 PPM                                | 6| 6| 6| 6| 6| 6| 6| 6| 6| 7| 7| 7| 7| 7| 7| 7| 7| 7| 7| 8| 8| 8| 8| 8| 8|             
                                           | 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
      Sarcoma, Metastatic, Skin            |                                                                          |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Glands, Adenoma                      |                                                                          |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                                          |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                            +                                   +         |             
      Adenocarcinoma                       |                                                                          |             
      Adenoma                              |                            X                                   X         |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                      X   |             
      Lymphoma Malignant Mixed             | X                                                                        |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  67                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 3| 7| 7| 7| 7| 7| 7| 6| 5| 7| 7| 6| 7| 7| 7| 1| 5| 7| 7| 5|             
                             DAY ON TEST   | 2| 2| 2| 5| 1| 1| 2| 2| 2| 2| 2| 2| 9| 5| 2| 2| 9| 2| 2| 2| 0| 5| 2| 2| 3|             
                                           | 5| 5| 5| 8| 8| 6| 5| 9| 5| 5| 6| 5| 3| 2| 5| 6| 2| 5| 5| 6| 0| 6| 5| 6| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 ALIMENTARY SYSTEM                         |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Esophagus                               | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Gallbladder                             | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Colon                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Rectum                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Large, Cecum                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Duodenum               | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  A  +  +  +  A|             
                                            __________________________________________________________________________|             
   Intestine Small, Jejunum                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +|             
                                            __________________________________________________________________________|             
   Intestine Small, Ileum                  | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Liver                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Hemangiosarcoma                      |                                                                          |             
      Hemangiosarcoma, Multiple            |                                                 X                        |             
      Hepatocellular Carcinoma             |             X        X                 X                                 |             
      Hepatocellular Adenoma               |                      X     X  X        X                                 |             
      Hepatocellular Adenoma, Multiple     |                                              X                           |             
                                            __________________________________________________________________________|             
   Mesentery                               |                                                                          |             
                                            __________________________________________________________________________|             
   Pancreas                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Salivary Glands                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Stomach, Forestomach                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Squamous Cell Carcinoma              |                                                                          |             
                                            __________________________________________________________________________|             
   Stomach, Glandular                      | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 CARDIOVASCULAR SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Heart                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 ENDOCRINE SYSTEM                          |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Adrenal Cortex                          | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcapsular, Adenoma                 |                                                    X                     |             
                                            __________________________________________________________________________|             
   Adrenal Medulla                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Pheochromocytoma Benign              |                                                                X         |             
                                            __________________________________________________________________________|             
   Islets, Pancreatic                      |                                                    +                     |             
                                            __________________________________________________________________________|             
   Parathyroid Gland                       | +  +  +  M  +  M  +  +  M  +  +  +  M  M  +  M  +  M  +  +  +  M  +  +  +|             
                                            __________________________________________________________________________|             
   Pituitary Gland                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  M  +  +  +  +  +|             
      Pars Distalis, Adenoma               |                         X                                                |             
                                            __________________________________________________________________________|             
   Thyroid Gland                           | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Bilateral, Follicular Cell, Adenoma  |                                                       X                  |             
      Follicular Cell, Adenoma             |                         X  X              X                              |             
 _____________________________________________________________________________________________________________________|             
 GENERAL BODY SYSTEM                       |                                                                          |             
                                           |                                                                          |             
    None                                   |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Coagulating Gland                       |                                                                          |             
                                            __________________________________________________________________________|             
   Epididymis                              | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Penis                                   |                                        +                                +|             
 _____________________________________________________________________________________________________________________|             

                                                             Page  68                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 3| 7| 7| 7| 7| 7| 7| 6| 5| 7| 7| 6| 7| 7| 7| 1| 5| 7| 7| 5|             
                             DAY ON TEST   | 2| 2| 2| 5| 1| 1| 2| 2| 2| 2| 2| 2| 9| 5| 2| 2| 9| 2| 2| 2| 0| 5| 2| 2| 3|             
                                           | 5| 5| 5| 8| 8| 6| 5| 9| 5| 5| 6| 5| 3| 2| 5| 6| 2| 5| 5| 6| 0| 6| 5| 6| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 GENITAL SYSTEM - cont                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Preputial Gland                         | +  +                          +                    +  +           +      |             
                                            __________________________________________________________________________|             
   Prostate                                | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Seminal Vesicle                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Testes                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 HEMATOPOIETIC SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone Marrow                             | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node                              |                +                    +                          +         |             
      Inguinal, Lymphoma Malignant Mixed   |                                                                          |             
      Lumbar, Lymphoma Malignant Mixed     |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Bronchial                   | +  M  +  +  +  M  +  +  M  +  +  +  M  +  +  M  M  M  +  M  M  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lymph Node, Mandibular                  | +  +  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  M  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mesenteric                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Lymph Node, Mediastinal                 | M  M  M  +  +  +  M  M  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
                                            __________________________________________________________________________|             
   Spleen                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Sarcoma, Metastatic, Skin            | X                                                                        |             
                                            __________________________________________________________________________|             
   Thymus                                  | +  +  M  +  M  +  +  +  +  +  M  +  +  +  +  +  +  +  +  +  M  +  +  +  +|             
      Lymphoma Malignant Mixed             |                                                                          |             
 _____________________________________________________________________________________________________________________|             
 INTEGUMENTARY SYSTEM                      |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Mammary Gland                           | M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M  M|             
                                            __________________________________________________________________________|             
   Skin                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Subcutaneous Tissue, Sarcoma         | X                                                                        |             
 _____________________________________________________________________________________________________________________|             
 MUSCULOSKELETAL SYSTEM                    |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Bone                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 NERVOUS SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Brain                                   | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM                        |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Larynx                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Lung                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Alveolar/Bronchiolar Adenoma         |    X  X              X        X     X     X                          X   |             
      Alveolar/Bronchiolar Adenoma,        |                                                                          |             
          Multiple                         |          X                                   X     X                     |             
      Alveolar/Bronchiolar Carcinoma       | X        X                                                           X   |             
      Hepatocellular Carcinoma, Metastatic,|                                                                          |             
           Liver                           |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  69                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 _____________________________________________________________________________________________________________________              
                                           | 7| 7| 7| 5| 7| 3| 7| 7| 7| 7| 7| 7| 6| 5| 7| 7| 6| 7| 7| 7| 1| 5| 7| 7| 5|             
                             DAY ON TEST   | 2| 2| 2| 5| 1| 1| 2| 2| 2| 2| 2| 2| 9| 5| 2| 2| 9| 2| 2| 2| 0| 5| 2| 2| 3|             
                                           | 5| 5| 5| 8| 8| 6| 5| 9| 5| 5| 6| 5| 3| 2| 5| 6| 2| 5| 5| 6| 0| 6| 5| 6| 4|             
 _____________________________________________________________________________________________________________________|             
                                           | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
   B6C3F1 MICE MALE                        | 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0|             
                               ANIMAL ID   | 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 3| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4| 4|             
    150 PPM                                | 8| 8| 8| 8| 9| 9| 9| 9| 9| 9| 9| 9| 9| 9| 0| 0| 0| 0| 0| 0| 0| 0| 0| 0| 1|             
                                           | 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0|             
 _____________________________________________________________________________________________________________________|             
 RESPIRATORY SYSTEM - cont                 |                                                                          |             
                                           |                                                                          |             
      Sarcoma, Metastatic, Skin            | X                                                                        |             
                                            __________________________________________________________________________|             
   Nose                                    | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Glands, Adenoma                      |                                                                          |             
                                            __________________________________________________________________________|             
   Trachea                                 | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SPECIAL SENSES SYSTEM                     |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Eye                                     |                                                             +     +      |             
                                            __________________________________________________________________________|             
   Harderian Gland                         |                      +                                   +        +  +   |             
      Adenocarcinoma                       |                      X                                                   |             
      Adenoma                              |                                                          X        X  X   |             
 _____________________________________________________________________________________________________________________|             
 URINARY SYSTEM                            |                                                                          |             
                                           |                                                                          |             
                                            __________________________________________________________________________|             
   Kidney                                  | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
                                            __________________________________________________________________________|             
   Urinary Bladder                         | +  +  +  +  +  +  +  +  +  +  +  +  A  +  +  +  +  +  +  +  +  +  +  +  +|             
 _____________________________________________________________________________________________________________________|             
 SYSTEMIC LESIONS                          |                                                                          |             
                                            __________________________________________________________________________|             
   Multiple Organs                         | +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +  +|             
      Lymphoma Malignant Lymphocytic       |                                                                          |             
      Lymphoma Malignant Mixed             |                                                                          |             
 _____________________________________________________________________________________________________________________|             

                                                             Page  70                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 3| 0| 2|                                                                 |            |
                             DAY ON TEST   | 0| 9| 9|                                                                 |            |
                                           | 0| 6| 6|                                                                 |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0|                                                                 |     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0|                                                                 |     T      |
                               ANIMAL ID   | 4| 4| 4|                                                                 |     A      |
    150 PPM                                | 1| 1| 1|                                                                 |     L      |
                                           | 1| 2| 6|                                                                 |            |
 __________________________________________________________________________________________________________________________________ 
 ALIMENTARY SYSTEM                         |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Esophagus                               | +  +  +                                                                  |  53        |
                                            __________________________________________________________________________|____________|
   Gallbladder                             | +  +  +                                                                  |  46        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Colon                  | +  +  A                                                                  |  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Rectum                 | A  +  A                                                                  |  49        |
                                            __________________________________________________________________________|____________|
   Intestine Large, Cecum                  | A  +  A                                                                  |  43        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Duodenum               | A  +  A                                                                  |  43        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Jejunum                | A  +  A                                                                  |  43        |
                                            __________________________________________________________________________|____________|
   Intestine Small, Ileum                  | A  A  A                                                                  |  43        |
                                            __________________________________________________________________________|____________|
   Liver                                   | +  +  +                                                                  |  53        |
      Hemangiosarcoma                      |                                                                          |          2 |
      Hemangiosarcoma, Multiple            |                                                                          |          1 |
      Hepatocellular Carcinoma             |                                                                          |          9 |
      Hepatocellular Adenoma               |                                                                          |         13 |
      Hepatocellular Adenoma, Multiple     |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Mesentery                               |                                                                          |   2        |
                                            __________________________________________________________________________|____________|
   Pancreas                                | +  +  A                                                                  |  49        |
                                            __________________________________________________________________________|____________|
   Salivary Glands                         | +  +  +                                                                  |  53        |
                                            __________________________________________________________________________|____________|
   Stomach, Forestomach                    | +  +  A                                                                  |  49        |
      Squamous Cell Carcinoma              |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Stomach, Glandular                      | +  +  A                                                                  |  49        |
 _____________________________________________________________________________________________________________________|            |
 CARDIOVASCULAR SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Heart                                   | +  +  +                                                                  |  53        |
 _____________________________________________________________________________________________________________________|            |
 ENDOCRINE SYSTEM                          |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Adrenal Cortex                          | +  +  +                                                                  |  51        |
      Subcapsular, Adenoma                 |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Adrenal Medulla                         | +  +  +                                                                  |  51        |
      Pheochromocytoma Benign              |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Islets, Pancreatic                      |                                                                          |   1        |
                                            __________________________________________________________________________|____________|
   Parathyroid Gland                       | +  +  +                                                                  |  39        |
                                            __________________________________________________________________________|____________|
   Pituitary Gland                         | +  +  +                                                                  |  47        |
      Pars Distalis, Adenoma               |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Thyroid Gland                           | +  +  +                                                                  |  53        |
      Bilateral, Follicular Cell, Adenoma  |                                                                          |          1 |
      Follicular Cell, Adenoma             |                                                                          |          4 |
 _____________________________________________________________________________________________________________________|            |
 GENERAL BODY SYSTEM                       |                                                                          |            |
                                           |                                                                          |            |
    None                                   |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  71                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 3| 0| 2|                                                                 |            |
                             DAY ON TEST   | 0| 9| 9|                                                                 |            |
                                           | 0| 6| 6|                                                                 |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0|                                                                 |     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0|                                                                 |     T      |
                               ANIMAL ID   | 4| 4| 4|                                                                 |     A      |
    150 PPM                                | 1| 1| 1|                                                                 |     L      |
                                           | 1| 2| 6|                                                                 |            |
 __________________________________________________________________________________________________________________________________ 
 GENITAL SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Coagulating Gland                       |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Epididymis                              | +  +  +                                                                  |  53        |
                                            __________________________________________________________________________|____________|
   Penis                                   |       +                                                                  |   5        |
                                            __________________________________________________________________________|____________|
   Preputial Gland                         |                                                                          |  12        |
                                            __________________________________________________________________________|____________|
   Prostate                                | +  +  +                                                                  |  53        |
                                            __________________________________________________________________________|____________|
   Seminal Vesicle                         | +  +  +                                                                  |  53        |
                                            __________________________________________________________________________|____________|
   Testes                                  | +  +  +                                                                  |  53        |
 _____________________________________________________________________________________________________________________|            |
 HEMATOPOIETIC SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone Marrow                             | +  +  +                                                                  |  52        |
                                            __________________________________________________________________________|____________|
   Lymph Node                              |                                                                          |   5        |
      Inguinal, Lymphoma Malignant Mixed   |                                                                          |          1 |
      Lumbar, Lymphoma Malignant Mixed     |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Bronchial                   | +  +  M                                                                  |  34        |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mandibular                  | +  +  +                                                                  |  48        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mesenteric                  | A  +  +                                                                  |  49        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Lymph Node, Mediastinal                 | +  +  +                                                                  |  41        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Spleen                                  | +  +  +                                                                  |  51        |
      Sarcoma, Metastatic, Skin            |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Thymus                                  | +  +  M                                                                  |  43        |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 INTEGUMENTARY SYSTEM                      |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Mammary Gland                           | M  M  M                                                                  |            |
                                            __________________________________________________________________________|____________|
   Skin                                    | +  +  +                                                                  |  52        |
      Subcutaneous Tissue, Sarcoma         |                                                                          |          1 |
 _____________________________________________________________________________________________________________________|            |
 MUSCULOSKELETAL SYSTEM                    |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Bone                                    | +  +  +                                                                  |  53        |
 _____________________________________________________________________________________________________________________|            |
 NERVOUS SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Brain                                   | +  +  +                                                                  |  53        |
 _____________________________________________________________________________________________________________________|            |
 RESPIRATORY SYSTEM                        |                                                                          |            |
                                           |                                                                          |            |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  72                                                               
NTP Experiment-Test: 05185-04                        NEOPLASMS BY INDIVIDUAL ANIMAL                               Report: PEIRPT04
Study Type: CHRONIC                                          ISOBUTYL NITRITE                                     Date: 03/17/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 18:40:55  
                                                                                                                                    
 __________________________________________________________________________________________________________________________________ 
                                           | 3| 0| 2|                                                                 |            |
                             DAY ON TEST   | 0| 9| 9|                                                                 |            |
                                           | 0| 6| 6|                                                                 |            |
 _____________________________________________________________________________________________________________________|     T (*)  |
                                           | 0| 0| 0|                                                                 |     O      |
   B6C3F1 MICE MALE                        | 0| 0| 0|                                                                 |     T      |
                               ANIMAL ID   | 4| 4| 4|                                                                 |     A      |
    150 PPM                                | 1| 1| 1|                                                                 |     L      |
                                           | 1| 2| 6|                                                                 |            |
 __________________________________________________________________________________________________________________________________ 
 RESPIRATORY SYSTEM - cont                 |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Larynx                                  | +  +  +                                                                  |  50        |
                                            __________________________________________________________________________|____________|
   Lung                                    | +  +  +                                                                  |  53        |
      Alveolar/Bronchiolar Adenoma         |                                                                          |         12 |
      Alveolar/Bronchiolar Adenoma,        |                                                                          |            |
          Multiple                         |                                                                          |          5 |
      Alveolar/Bronchiolar Carcinoma       |                                                                          |          4 |
      Hepatocellular Carcinoma, Metastatic,|                                                                          |            |
           Liver                           |                                                                          |          1 |
      Sarcoma, Metastatic, Skin            |                                                                          |          1 |
                                            __________________________________________________________________________|____________|
   Nose                                    | +  +  +                                                                  |  53        |
      Glands, Adenoma                      |       X                                                                  |          1 |
                                            __________________________________________________________________________|____________|
   Trachea                                 | +  +  +                                                                  |  52        |
 _____________________________________________________________________________________________________________________|            |
 SPECIAL SENSES SYSTEM                     |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Eye                                     |                                                                          |   2        |
                                            __________________________________________________________________________|____________|
   Harderian Gland                         |                                                                          |   6        |
      Adenocarcinoma                       |                                                                          |          1 |
      Adenoma                              |                                                                          |          5 |
 _____________________________________________________________________________________________________________________|            |
 URINARY SYSTEM                            |                                                                          |            |
                                           |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Kidney                                  | +  +  +                                                                  |  53        |
                                            __________________________________________________________________________|____________|
   Urinary Bladder                         | +  +  A                                                                  |  50        |
 __________________________________________________________________________________________________________________________________ 
 SYSTEMIC LESIONS                          |                                                                          |            |
                                            __________________________________________________________________________|____________|
   Multiple Organs                         | +  +  +                                                                  |  53        |
      Lymphoma Malignant Lymphocytic       |                                                                          |          1 |
      Lymphoma Malignant Mixed             |                                                                          |          1 |
 __________________________________________________________________________________________________________________________________ 

                         * : Total animals with tissue examined microscopically; total animals with tumor                           
                         + : Tissue examined microscopically                      M : Missing tissue                                
                         X : Lesion present                                       A : Autolysis precludes evaluation                
                         I : Insufficient tissue                              BLANK : Not examined microscopically                  

                                                             Page  73                                                               
                                  ------------------------------------------------------------                                      
                                  ----------              END OF REPORT             ----------                                      
                                  ------------------------------------------------------------