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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                                                               
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