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TDMS Study 05185-04 Pathology Tables


                              INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)
                                                       ISOBUTYL NITRITE (IBN)


NTP Experiment-Test: 05185-04                                                                                     Report: PEIRPT05
Study Type: CHRONIC                                                                                               Date: 05/20/95
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49




       Facility:  I. I. T. Research Institute

       Chemical CAS #:  542-56-3

       Lock Date:  08/20/92

       Cage Range:  All

       Reasons For Removal:    All

       Removal Date Range:     All

       Treatment Groups:       Include All
































a  Number of animals examined microscopically at site and number of animals with lesion

                                                             Page   1

NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially in Study                          60           60           60           60                                     
  Scheduled Sacrifice                                  9            9            9           10                                     
  Early Deaths                                                                                                                      
    Natural Death                                     16            6            8           10                                     
    Moribund Sacrifice                                 3            3            6            2                                     
    Accidently Killed                                                                         1                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                32           42           36           37                                     
  Other                                                                          1                                                  
  Animals Examined Microscopically                    60           60           59           60                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Esophagus                                          (60)         (58)         (59)         (57)                                   
      Squamous Cell Carcinoma                                       1 (2%)                                                          
   Gallbladder                                        (55)         (55)         (54)         (51)                                   
   Intestine Large, Colon                             (60)         (60)         (59)         (56)                                   
   Intestine Large, Rectum                            (57)         (60)         (59)         (57)                                   
      Schwannoma Malignant, Metastatic, Skin           1 (2%)                                                                       
   Intestine Large, Cecum                             (57)         (58)         (59)         (55)                                   
   Intestine Small, Duodenum                          (51)         (59)         (58)         (52)                                   
   Intestine Small, Jejunum                           (53)         (59)         (56)         (55)                                   
   Intestine Small, Ileum                             (53)         (57)         (59)         (54)                                   
   Liver                                              (60)         (60)         (59)         (60)                                   
      Hepatocellular Carcinoma                         3 (5%)       5 (8%)       2 (3%)       5 (8%)                                
      Hepatocellular Carcinoma, Multiple               1 (2%)                                                                       
      Hepatocellular Adenoma                           7 (12%)     10 (17%)      2 (3%)       4 (7%)                                
      Hepatocellular Adenoma, Multiple                                           5 (8%)       2 (3%)                                
      Hepatocholangiocarcinoma                         1 (2%)                                                                       
      Histiocytic Sarcoma                              2 (3%)       1 (2%)                    1 (2%)                                
   Mesentery                                          (7)          (4)          (3)          (2)                                    
      Hepatocellular Carcinoma, Metastatic, Liver      1 (14%)                                                                      
   Pancreas                                           (60)         (60)         (59)         (60)                                   
      Hepatocholangiocarcinoma, Metastatic, Liver      1 (2%)                                                                       
      Schwannoma Malignant, Metastatic, Skin           1 (2%)                                                                       
   Salivary Glands                                    (60)         (60)         (59)         (60)                                   
   Stomach, Forestomach                               (60)         (60)         (59)         (59)                                   
   Stomach, Glandular                                 (60)         (60)         (59)         (59)                                   
   Tooth                                              (1)                       (1)          (1)                                    
      Odontoma                                                                   1 (100%)     1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   2                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (60)         (60)         (59)         (60)                                   
      Hepatocholangiocarcinoma, Metastatic, Liver      1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (59)         (60)         (59)         (59)                                   
   Adrenal Medulla                                    (55)         (58)         (54)         (57)                                   
      Pheochromocytoma Malignant                                    1 (2%)                                                          
      Pheochromocytoma Benign                                                    2 (4%)       2 (4%)                                
   Islets, Pancreatic                                 (2)          (2)          (3)          (3)                                    
      Adenoma                                                       1 (50%)                                                         
   Pituitary Gland                                    (56)         (56)         (59)         (57)                                   
      Pars Distalis, Adenoma                          12 (21%)     19 (34%)     18 (31%)     13 (23%)                               
      Pars Intermedia, Adenoma                         2 (4%)       2 (4%)                                                          
   Thyroid Gland                                      (60)         (60)         (59)         (60)                                   
      Follicular Cell, Adenoma                         4 (7%)       3 (5%)       2 (3%)       2 (3%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Ovary                                              (58)         (59)         (55)         (59)                                   
      Cystadenoma                                      1 (2%)                    2 (4%)       1 (2%)                                
      Granulosa Cell Tumor Malignant                                             1 (2%)                                             
      Granulosa Cell Tumor Benign                                                             1 (2%)                                
   Oviduct                                                                      (1)                                                 
   Uterus                                             (60)         (60)         (58)         (59)                                   
      Deciduoma NOS                                                 1 (2%)                                                          
      Hemangioma                                       1 (2%)                                                                       
      Histiocytic Sarcoma                              2 (3%)       2 (3%)                    1 (2%)                                
      Leiomyosarcoma                                                             1 (2%)       1 (2%)                                
      Myxoma                                                                                  1 (2%)                                
      Polyp Stromal                                    3 (5%)       2 (3%)                    1 (2%)                                
      Sarcoma Stromal                                  1 (2%)                                                                       
   Vagina                                             (1)                       (1)          (2)                                    
      Histiocytic Sarcoma                              1 (100%)                                                                     
      Squamous Cell Carcinoma                                                                 1 (50%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   3                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (60)         (60)         (59)         (60)                                   
   Lymph Node                                         (4)          (5)          (8)          (6)                                    
      Inguinal, Histiocytic Sarcoma                    1 (25%)                                                                      
      Lumbar, Histiocytic Sarcoma                      1 (25%)                                                                      
      Pancreatic, Hepatocholangiocarcinoma,                                                                                         
          Metastatic, Liver                            1 (25%)                                                                      
      Renal, Histiocytic Sarcoma                       1 (25%)                                                                      
   Lymph Node, Bronchial                              (28)         (42)         (40)         (38)                                   
   Lymph Node, Mandibular                             (58)         (57)         (57)         (55)                                   
      Histiocytic Sarcoma                              1 (2%)                                                                       
   Lymph Node, Mesenteric                             (60)         (59)         (58)         (55)                                   
      Hemangioma                                                                              1 (2%)                                
      Histiocytic Sarcoma                                                                     1 (2%)                                
   Lymph Node, Mediastinal                            (58)         (51)         (52)         (53)                                   
      Histiocytic Sarcoma                              1 (2%)                                                                       
   Spleen                                             (60)         (60)         (59)         (59)                                   
      Hemangiosarcoma                                  1 (2%)       1 (2%)                                                          
      Histiocytic Sarcoma                              1 (2%)                                                                       
   Thymus                                             (56)         (56)         (57)         (51)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (58)         (60)         (59)         (60)                                   
      Adenocarcinoma                                                             1 (2%)                                             
      Adenoma                                                                    1 (2%)                                             
   Skin                                               (60)         (60)         (59)         (60)                                   
      Subcutaneous Tissue, Fibrosarcoma                                          1 (2%)                                             
      Subcutaneous Tissue, Hemangioma                  1 (2%)                                                                       
      Subcutaneous Tissue, Hemangiosarcoma                          1 (2%)                                                          
      Subcutaneous Tissue, Sarcoma                     1 (2%)                    1 (2%)                                             
      Subcutaneous Tissue, Schwannoma Malignant        1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (60)         (60)         (59)         (60)                                   
      Hemangioma                                                    1 (2%)                                                          
      Schwannoma Malignant, Metastatic, Skin           1 (2%)                                                                       
   Skeletal Muscle                                                 (3)          (1)          (1)                                    
      Hemangiosarcoma                                               1 (33%)                                                         
      Osteosarcoma                                                  1 (33%)                                                         
      Sarcoma                                                                                 1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                             Page   4                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (60)         (60)         (59)         (60)                                   
      Adenoma                                                                    1 (2%)                                             
      Alveolar/Bronchiolar Adenoma                     4 (7%)      13 (22%)      7 (12%)     17 (28%)                               
      Alveolar/Bronchiolar Adenoma, Multiple                        3 (5%)       1 (2%)       2 (3%)                                
      Alveolar/Bronchiolar Carcinoma                   2 (3%)       2 (3%)       2 (3%)       2 (3%)                                
      Hepatocellular Carcinoma, Metastatic, Liver      1 (2%)       1 (2%)       2 (3%)       3 (5%)                                
      Hepatocholangiocarcinoma, Metastatic, Liver      1 (2%)                                                                       
      Histiocytic Sarcoma                                                                     1 (2%)                                
      Osteosarcoma, Metastatic, Skeletal Muscle                     1 (2%)                                                          
      Mediastinum, Hepatocellular Carcinoma,                                                                                        
          Metastatic, Liver                                                      1 (2%)                                             
      Mediastinum, Hepatocholangiocarcinoma,                                                                                        
          Metastatic, Liver                            1 (2%)                                                                       
   Nose                                               (60)         (60)         (59)         (60)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Harderian Gland                                                 (1)          (2)          (2)                                    
      Adenoma                                                       1 (100%)     1 (50%)      2 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (60)         (60)         (59)         (60)                                   
      Histiocytic Sarcoma                                                                     1 (2%)                                
      Osteosarcoma, Metastatic, Skeletal Muscle                     1 (2%)                                                          
   Urinary Bladder                                    (58)         (59)         (57)         (57)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SYSTEMIC LESIONS                                                                                                                   
   Multiple Organs                                   *(60)        *(60)        *(59)        *(60)                                   
      Histiocytic Sarcoma                              2 (3%)       2 (3%)                    2 (3%)                                
      Lymphoma Malignant Histiocytic                   1 (2%)                                                                       
      Lymphoma Malignant Lymphocytic                   1 (2%)                    1 (2%)       3 (5%)                                
      Lymphoma Malignant Mixed                         5 (8%)       4 (7%)       9 (15%)      6 (10%)                               
      Lymphoma Malignant Undifferentiated Cell                      2 (3%)       1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
     *   Number of animals with any tissue examined microscopically                                                                 
                                                             Page   5                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            38          48          39          42                                       
     Total Primary Neoplasms                           55          77          63          71                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 28          38          31          35                                       
     Total Benign Neoplasms                            35          55          43          50                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              17          18          19          19                                       
     Total Malignant Neoplasms                         20          21          20          21                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              3           2           2           3                                       
     Total Metastatic Neoplasm                         10           3           3           3                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms                                                                                           
   Uncertain Primary Site                                                                                                           
                                                                                                                                    
   Total Animals with Neoplasms Uncertain-                                                                                          
   Benign or Malignant                                              1                                                               
     Total Uncertain Neoplasms                                      1                                                               
                                                                                                                                    
____________________________________________________________________________________________________________________________________
a  Number of animals examined microscopically at site and number of animals with lesion                                             
b  Primary tumors: all tumors except metastatic tumors                                                                              
                                                             Page   6                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially in Study                          60           60           60           60                                     
  Scheduled Sacrifice                                 10           10           10            7                                     
  Early Deaths                                                                                                                      
    Natural Death                                     10            8           11           17                                     
    Accidently Killed                                  2                                      2                                     
    Moribund Sacrifice                                 1            7            4            4                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                37           35           35           30                                     
  Animals Examined Microscopically                    60           60           60           60                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Intestine Small, Jejunum                           (52)         (55)         (56)         (50)                                   
      Adenocarcinoma                                                             1 (2%)                                             
      Adenocarcinoma, Metastatic, Intestine Small,                                                                                  
           Jejunum                                                               1 (2%)                                             
   Intestine Small, Ileum                             (55)         (55)         (53)         (50)                                   
      Adenocarcinoma, Metastatic, Intestine Small,                                                                                  
           Jejunum                                                               1 (2%)                                             
   Liver                                              (60)         (60)         (60)         (60)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                     1 (2%)                                                          
      Cholangiocarcinoma                                                         1 (2%)                                             
      Hemangiosarcoma                                  1 (2%)       1 (2%)       1 (2%)       2 (3%)                                
      Hemangiosarcoma, Multiple                        1 (2%)       1 (2%)                    1 (2%)                                
      Hepatocellular Carcinoma                        10 (17%)      6 (10%)      9 (15%)      9 (15%)                               
      Hepatocellular Carcinoma, Multiple               3 (5%)       1 (2%)       2 (3%)                                             
      Hepatocellular Adenoma                          11 (18%)     16 (27%)     17 (28%)     14 (23%)                               
      Hepatocellular Adenoma, Multiple                 5 (8%)                    1 (2%)       2 (3%)                                
   Mesentery                                                       (1)          (5)          (2)                                    
      Cholangiocarcinoma, Metastatic, Liver                                      1 (20%)                                            
      Hemangiosarcoma                                                            1 (20%)                                            
   Pancreas                                           (60)         (59)         (60)         (56)                                   
   Salivary Glands                                    (60)         (60)         (60)         (60)                                   
   Stomach, Forestomach                               (59)         (59)         (59)         (56)                                   
      Squamous Cell Carcinoma                                                                 1 (2%)                                
   Tooth                                              (3)                       (1)          (1)                                    
      Odontoma                                         1 (33%)                   1 (100%)     1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   7                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (60)         (60)         (60)         (60)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                     1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (59)         (59)         (58)         (58)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                                  1 (2%)                                             
      Subcapsular, Adenoma                                          1 (2%)                    1 (2%)                                
   Adrenal Medulla                                    (59)         (59)         (58)         (58)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                                  1 (2%)                                             
      Pheochromocytoma Benign                                       2 (3%)                    1 (2%)                                
   Islets, Pancreatic                                 (5)          (3)          (9)          (1)                                    
      Adenoma                                          2 (40%)      1 (33%)      2 (22%)                                            
   Pituitary Gland                                    (56)         (56)         (54)         (54)                                   
      Pars Distalis, Adenoma                                                     1 (2%)       1 (2%)                                
      Pars Intermedia, Adenoma                         1 (2%)       1 (2%)                                                          
   Thyroid Gland                                      (60)         (60)         (60)         (60)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                     1 (2%)                                                          
      Bilateral, Follicular Cell, Adenoma                                                     1 (2%)                                
      C-Cell, Carcinoma                                                          1 (2%)                                             
      Follicular Cell, Adenoma                         1 (2%)                                 4 (7%)                                
      Follicular Cell, Carcinoma                                    1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Epididymis                                         (60)         (60)         (60)         (60)                                   
      Cholangiocarcinoma, Metastatic, Liver                                      1 (2%)                                             
   Seminal Vesicle                                    (60)         (60)         (60)         (60)                                   
   Testes                                             (60)         (60)         (60)         (60)                                   
      Interstitial Cell, Adenoma                                                 1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   8                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (60)         (60)         (59)         (59)                                   
      Hemangiosarcoma                                               1 (2%)                                                          
   Lymph Node                                         (1)          (5)          (5)          (5)                                    
      Inguinal, Alveolar/Bronchiolar Carcinoma,                                                                                     
           Metastatic, Lung                                         1 (20%)                                                         
      Inguinal, Cholangiocarcinoma, Metastatic,                                                                                     
           Liver                                                                 1 (20%)                                            
   Lymph Node, Bronchial                              (33)         (45)         (26)         (39)                                   
   Lymph Node, Mandibular                             (49)         (59)         (60)         (55)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                     1 (2%)                                                          
   Lymph Node, Mesenteric                             (57)         (57)         (57)         (56)                                   
      Cholangiocarcinoma, Metastatic, Liver                                      1 (2%)                                             
   Lymph Node, Mediastinal                            (48)         (47)         (48)         (46)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                     1 (2%)                                                          
      Cholangiocarcinoma, Metastatic, Liver                                      1 (2%)                                             
      Hepatocellular Carcinoma, Metastatic, Liver                   1 (2%)                                                          
   Spleen                                             (60)         (60)         (59)         (58)                                   
      Hemangioma                                       1 (2%)                                                                       
      Hemangiosarcoma                                                            1 (2%)                                             
      Sarcoma, Metastatic, Skin                                                               1 (2%)                                
   Thymus                                             (55)         (56)         (48)         (50)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                     1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Skin                                               (60)         (60)         (59)         (59)                                   
      Subcutaneous Tissue, Alveolar/Bronchiolar                                                                                     
          Carcinoma, Metastatic, Lung                                            1 (2%)                                             
      Subcutaneous Tissue, Sarcoma                                                            1 (2%)                                
      Subcutaneous Tissue, Schwannoma Malignant,                                                                                    
           Multiple                                                              1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (60)         (60)         (60)         (60)                                   
      Mandible, Alveolar/Bronchiolar Carcinoma,                                                                                     
           Metastatic, Lung                                         1 (2%)                                                          
      Rib, Alveolar/Bronchiolar Carcinoma,                                                                                          
          Metastatic, Lung                                          1 (2%)                                                          
   Skeletal Muscle                                                 (1)          (1)                                                 
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
                                                             Page   9                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
MUSCULOSKELETAL SYSTEM - cont                                                                                                       
           Lung                                                     1 (100%)                                                        
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Larynx                                             (60)         (60)         (59)         (57)                                   
   Lung                                               (60)         (60)         (59)         (60)                                   
      Alveolar/Bronchiolar Adenoma                     8 (13%)     11 (18%)     10 (17%)     12 (20%)                               
      Alveolar/Bronchiolar Adenoma, Multiple                        3 (5%)       3 (5%)       5 (8%)                                
      Alveolar/Bronchiolar Carcinoma                   1 (2%)       5 (8%)       4 (7%)       4 (7%)                                
      Alveolar/Bronchiolar Carcinoma, Multiple                      1 (2%)       1 (2%)                                             
      Cholangiocarcinoma, Metastatic, Liver                                      1 (2%)                                             
      Hepatocellular Carcinoma, Metastatic, Liver      5 (8%)       6 (10%)      4 (7%)       1 (2%)                                
      Sarcoma, Metastatic, Skin                                                               1 (2%)                                
      Mediastinum, Cholangiocarcinoma, Metastatic,                                                                                  
           Liver                                                                 1 (2%)                                             
   Nose                                               (60)         (60)         (60)         (60)                                   
      Glands, Adenoma                                                                         1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Harderian Gland                                    (5)          (1)          (3)          (6)                                    
      Adenocarcinoma                                                                          1 (17%)                               
      Adenoma                                          4 (80%)      1 (100%)     3 (100%)     5 (83%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (60)         (60)         (60)         (60)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                     1 (2%)                                                          
      Cholangiocarcinoma, Metastatic, Liver                                      1 (2%)                                             
      Hepatocellular Carcinoma, Metastatic, Liver                                1 (2%)                                             
      Renal Tubule, Adenoma                                         1 (2%)                                                          
   Urinary Bladder                                    (60)         (58)         (59)         (57)                                   
      Cholangiocarcinoma, Metastatic, Liver                                      1 (2%)                                             
                                                                                                                                    
                                                             Page  10                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 SYSTEMIC LESIONS                                                                                                                   
   Multiple Organs                                   *(60)        *(60)        *(60)        *(60)                                   
      Lymphoma Malignant Lymphocytic                                             1 (2%)       1 (2%)                                
      Lymphoma Malignant Mixed                         1 (2%)       3 (5%)       1 (2%)       1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
     *   Number of animals with any tissue examined microscopically                                                                 
                                                             Page  11                                                               
NTP Experiment-Test: 05185-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 11:28:49  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            38          39          43          42                                       
     Total Primary Neoplasms                           51          57          64          69                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 28          31          33          36                                       
     Total Benign Neoplasms                            34          37          39          48                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              17          19          22          17                                       
     Total Malignant Neoplasms                         17          20          25          21                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              5           7           7           2                                       
     Total Metastatic Neoplasm                          5          18          19           3                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms                                                                                           
   Uncertain Primary Site                                                                                                           
                                                                                                                                    
   Total Animals with Neoplasms Uncertain-                                                                                          
   Benign or Malignant                                                                                                              
     Total Uncertain Neoplasms                                                                                                      
                                                                                                                                    
____________________________________________________________________________________________________________________________________
a  Number of animals examined microscopically at site and number of animals with lesion                                             
b  Primary tumors: all tumors except metastatic tumors                                                                              
                                                             Page  12                                                               
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                             ----------              END OF REPORT             ----------                                           
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