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TDMS Study 05185-03 Pathology Tables


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


NTP Experiment-Test: 05185-03                                                                                     Report: PEIRPT05
Study Type: CHRONIC                                                                                               Date: 05/20/95
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26




       Facility:  I. I. T. Research Institute

       Chemical CAS #:  542-56-3

       Lock Date:  05/22/92

       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: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially in Study                          56           56           56           56                                     
  Scheduled Sacrifice                                 10           10           10           10                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                13            4            7            6                                     
    Natural Death                                      4            6            8            7                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                29           35           30           33                                     
    Natural Death                                                                1                                                  
  Missing                                                           1                                                               
  Animals Examined Microscopically                    56           55           56           56                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Intestine Large, Cecum                             (56)         (54)         (53)         (53)                                   
   Intestine Small, Ileum                             (54)         (51)         (50)         (51)                                   
   Liver                                              (56)         (54)         (56)         (56)                                   
      Hepatocellular Adenoma                                        1 (2%)                                                          
      Histiocytic Sarcoma                                           1 (2%)       1 (2%)                                             
   Pancreas                                           (56)         (55)         (56)         (56)                                   
   Stomach, Forestomach                               (56)         (55)         (56)         (56)                                   
   Stomach, Glandular                                 (56)         (54)         (55)         (56)                                   
   Tongue                                             (1)          (1)          (2)          (1)                                    
      Squamous Cell Carcinoma                          1 (100%)                  1 (50%)      1 (100%)                              
      Squamous Cell Papilloma                                       1 (100%)     1 (50%)                                            
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (56)         (55)         (56)         (56)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (56)         (55)         (56)         (56)                                   
      Adenoma                                                       1 (2%)                                                          
   Adrenal Medulla                                    (55)         (55)         (55)         (56)                                   
      Pheochromocytoma Complex                         2 (4%)                                                                       
      Pheochromocytoma Benign                                       3 (5%)       1 (2%)       2 (4%)                                
      Bilateral, Pheochromocytoma Malignant                         1 (2%)                                                          
   Islets, Pancreatic                                 (6)          (1)                       (1)                                    
      Adenoma                                          5 (83%)      1 (100%)                  1 (100%)                              
   Pituitary Gland                                    (56)         (53)         (55)         (56)                                   
                                                             Page   2                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ENDOCRINE SYSTEM - cont                                                                                                             
      Pars Distalis, Adenoma                          24 (43%)     16 (30%)     19 (35%)     17 (30%)                               
      Pars Distalis, Adenoma, Multiple                 2 (4%)                    1 (2%)       1 (2%)                                
      Pars Distalis, Carcinoma                         1 (2%)                    1 (2%)                                             
   Thyroid Gland                                      (56)         (55)         (56)         (56)                                   
      Bilateral, C-Cell, Adenoma                                    1 (2%)                                                          
      C-Cell, Adenoma                                  1 (2%)       3 (5%)       2 (4%)       3 (5%)                                
      C-Cell, Carcinoma                                             2 (4%)                                                          
      Follicular Cell, Carcinoma                                                              2 (4%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Clitoral Gland                                     (54)         (54)         (54)         (56)                                   
      Adenoma                                          1 (2%)       1 (2%)       1 (2%)       1 (2%)                                
      Carcinoma                                        1 (2%)                                                                       
      Bilateral, Adenoma                                                         1 (2%)                                             
   Ovary                                              (56)         (55)         (56)         (56)                                   
      Granulosa Cell Tumor Benign                                   1 (2%)                                                          
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Uterus                                             (56)         (55)         (56)         (56)                                   
      Polyp Stromal                                    1 (2%)       5 (9%)       3 (5%)       2 (4%)                                
      Sarcoma Stromal                                  1 (2%)                                                                       
      Bilateral, Polyp Stromal                         1 (2%)                    3 (5%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (56)         (55)         (56)         (56)                                   
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Lymph Node                                         (1)          (1)                       (3)                                    
   Lymph Node, Bronchial                              (36)         (40)         (46)         (38)                                   
      Histiocytic Sarcoma                                                        1 (2%)                                             
      Rhabdomyosarcoma, Metastatic, Uncertain                                                                                       
          Primary Site                                                                        1 (3%)                                
   Lymph Node, Mandibular                             (55)         (55)         (53)         (53)                                   
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Lymph Node, Mesenteric                             (56)         (55)         (56)         (55)                                   
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Lymph Node, Mediastinal                            (54)         (54)         (51)         (53)                                   
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Spleen                                             (56)         (55)         (54)         (56)                                   
      Hemangiosarcoma                                                                         1 (2%)                                
                                                             Page   3                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - cont                                                                                                         
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Thymus                                             (54)         (53)         (55)         (54)                                   
      Histiocytic Sarcoma                                                        1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (56)         (55)         (56)         (56)                                   
      Adenocarcinoma                                   3 (5%)       1 (2%)       1 (2%)       1 (2%)                                
      Adenoma                                                       1 (2%)                    1 (2%)                                
      Fibroadenoma                                     9 (16%)      8 (15%)     16 (29%)     13 (23%)                               
      Fibroadenoma, Multiple                           3 (5%)       6 (11%)      4 (7%)                                             
   Skin                                               (56)         (55)         (56)         (56)                                   
      Squamous Cell Papilloma                                                                 1 (2%)                                
      Subcutaneous Tissue, Fibroma                                  2 (4%)                    1 (2%)                                
      Subcutaneous Tissue, Fibrosarcoma                1 (2%)                                                                       
      Subcutaneous Tissue, Lipoma                      1 (2%)                    1 (2%)                                             
      Tail, Squamous Cell Papilloma                    1 (2%)       1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (56)         (55)         (56)         (56)                                   
      Astrocytoma Benign                                                                      1 (2%)                                
      Carcinoma, Metastatic, Pituitary Gland           1 (2%)                    1 (2%)                                             
      Glioma Malignant                                 1 (2%)                    1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Larynx                                             (56)         (55)         (56)         (56)                                   
   Lung                                               (56)         (55)         (56)         (56)                                   
      Alveolar/Bronchiolar Adenoma                                  2 (4%)       2 (4%)       8 (14%)                               
      Alveolar/Bronchiolar Adenoma, Multiple                                                  2 (4%)                                
      Alveolar/Bronchiolar Carcinoma                                1 (2%)                    1 (2%)                                
      Mediastinum, Rhabdomyosarcoma, Metastatic,                                                                                    
           Uncertain Primary Site                                                             1 (2%)                                
   Nose                                               (56)         (55)         (55)         (56)                                   
____________________________________________________________________________________________________________________________________
                                                             Page   4                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (56)         (55)         (56)         (56)                                   
      Sarcoma                                                                    1 (2%)                                             
   Urinary Bladder                                    (56)         (54)         (55)         (52)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SYSTEMIC LESIONS                                                                                                                   
   Multiple Organs                                   *(56)        *(55)        *(56)        *(56)                                   
      Histiocytic Sarcoma                                           1 (2%)       1 (2%)                                             
      Leukemia Mononuclear                            15 (27%)      1 (2%)                    1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
     *   Number of animals with any tissue examined microscopically                                                                 
                                                             Page   5                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            44          36          37          35                                       
     Total Primary Neoplasms                           75          61          61          61                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 35          36          35          34                                       
     Total Benign Neoplasms                            49          54          55          54                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              22           7           6           7                                       
     Total Malignant Neoplasms                         26           7           6           7                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              1                       1           1                                       
     Total Metastatic Neoplasm                          1                       1           2                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms                                                   1                                       
   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   6                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially in Study                          56           56           56           56                                     
  Scheduled Sacrifice                                 10           10           10           10                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                21           12            5            8                                     
    Natural Death                                      8           11            4           10                                     
    Accidently Killed                                                            1                                                  
  Survivors                                                                                                                         
    Terminal Sacrifice                                17           23           36           28                                     
  Animals Examined Microscopically                    56           56           56           56                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Esophagus                                          (55)         (56)         (56)         (56)                                   
   Intestine Large, Colon                             (55)         (55)         (56)         (55)                                   
   Intestine Large, Rectum                            (54)         (54)         (55)         (55)                                   
   Intestine Large, Cecum                             (54)         (51)         (54)         (53)                                   
   Intestine Small, Duodenum                          (54)         (54)         (56)         (55)                                   
   Intestine Small, Jejunum                           (54)         (50)         (54)         (49)                                   
      Adenocarcinoma                                   1 (2%)                                                                       
   Intestine Small, Ileum                             (53)         (46)         (53)         (52)                                   
   Liver                                              (55)         (56)         (56)         (56)                                   
      Hepatocellular Carcinoma                                                   1 (2%)                                             
      Hepatocellular Adenoma                           1 (2%)       1 (2%)                    1 (2%)                                
      Histiocytic Sarcoma, Metastatic, Skin                                                   1 (2%)                                
      Sarcoma, Metastatic, Skin                        1 (2%)                                                                       
   Mesentery                                          (6)          (1)          (4)          (10)                                   
   Pancreas                                           (55)         (56)         (56)         (56)                                   
      Carcinoma, Metastatic, Kidney                    1 (2%)                                                                       
   Salivary Glands                                    (56)         (55)         (56)         (56)                                   
   Stomach, Forestomach                               (55)         (56)         (56)         (56)                                   
   Stomach, Glandular                                 (55)         (56)         (56)         (55)                                   
   Tongue                                                          (1)          (1)                                                 
      Squamous Cell Papilloma                                       1 (100%)                                                        
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (56)         (56)         (56)         (56)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                        1 (2%)                                 1 (2%)                                
      Schwannoma Malignant                                                       1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                             Page   7                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (55)         (56)         (56)         (56)                                   
   Adrenal Medulla                                    (54)         (55)         (56)         (56)                                   
      Pheochromocytoma Malignant                       1 (2%)       4 (7%)                    1 (2%)                                
      Pheochromocytoma Benign                          4 (7%)       8 (15%)      8 (14%)     14 (25%)                               
      Bilateral, Pheochromocytoma Benign               4 (7%)                                 1 (2%)                                
   Islets, Pancreatic                                 (8)          (9)          (5)          (5)                                    
      Adenoma                                          3 (38%)      6 (67%)      2 (40%)      4 (80%)                               
      Carcinoma                                        1 (13%)                   1 (20%)                                            
   Parathyroid Gland                                  (49)         (50)         (48)         (52)                                   
   Pituitary Gland                                    (55)         (56)         (56)         (55)                                   
      Pars Distalis, Adenoma                          30 (55%)     24 (43%)     27 (48%)     28 (51%)                               
      Pars Distalis, Adenoma, Multiple                              1 (2%)       3 (5%)       2 (4%)                                
      Pars Nervosa, Craniopharyngioma                                                         1 (2%)                                
   Thyroid Gland                                      (55)         (56)         (56)         (56)                                   
      C-Cell, Adenoma                                  1 (2%)       1 (2%)       5 (9%)       4 (7%)                                
      C-Cell, Carcinoma                                1 (2%)                                 1 (2%)                                
      Follicular Cell, Carcinoma                       1 (2%)       1 (2%)       2 (4%)       1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   Tissue NOS                                         (3)                                    (1)                                    
      Mediastinum, Carcinoma, Metastatic, Thyroid                                                                                   
          Gland                                        1 (33%)                                                                      
      Thoracic, Alveolar/Bronchiolar Carcinoma,                                                                                     
           Metastatic, Lung                            1 (33%)                                                                      
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Epididymis                                         (56)         (56)         (56)         (56)                                   
   Preputial Gland                                    (54)         (56)         (56)         (56)                                   
      Adenoma                                          3 (6%)       5 (9%)       3 (5%)       2 (4%)                                
      Carcinoma                                                                  1 (2%)                                             
      Histiocytic Sarcoma, Metastatic, Skin                                                   1 (2%)                                
   Prostate                                           (56)         (56)         (56)         (56)                                   
   Seminal Vesicle                                    (55)         (56)         (56)         (56)                                   
   Testes                                             (56)         (56)         (56)         (56)                                   
      Bilateral, Interstitial Cell, Adenoma           20 (36%)     26 (46%)     25 (45%)     27 (48%)                               
      Interstitial Cell, Adenoma                      14 (25%)      8 (14%)     13 (23%)     12 (21%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   8                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (55)         (55)         (56)         (56)                                   
   Lymph Node                                         (5)                                    (1)                                    
   Lymph Node, Bronchial                              (47)         (43)         (40)         (39)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                        1 (2%)                                 1 (3%)                                
      Carcinoma, Metastatic, Kidney                    1 (2%)                                                                       
   Lymph Node, Mandibular                             (55)         (55)         (56)         (56)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                                               1 (2%)                                
   Lymph Node, Mesenteric                             (55)         (56)         (56)         (54)                                   
   Lymph Node, Mediastinal                            (55)         (52)         (52)         (55)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                                               1 (2%)                                
      Carcinoma, Metastatic, Kidney                    1 (2%)                                                                       
      Carcinoma, Metastatic, Zymbal's Gland                                                   1 (2%)                                
      Sarcoma, Metastatic, Skin                        1 (2%)                                                                       
   Spleen                                             (56)         (55)         (56)         (55)                                   
      Fibroma                                                       1 (2%)                                                          
      Hemangiosarcoma                                  1 (2%)       1 (2%)                    2 (4%)                                
   Thymus                                             (51)         (56)         (55)         (54)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                        1 (2%)                                                                       
      Thymoma Benign                                                                          1 (2%)                                
      Thymoma Malignant                                             1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (52)         (53)         (56)         (53)                                   
      Fibroadenoma                                                  2 (4%)       1 (2%)                                             
   Skin                                               (56)         (56)         (56)         (56)                                   
      Keratoacanthoma                                  2 (4%)       2 (4%)       2 (4%)                                             
      Trichoepithelioma                                             1 (2%)                                                          
      Back, Squamous Cell Carcinoma                                              1 (2%)                                             
      Head, Basosquamous Tumor Benign                                            1 (2%)                                             
      Inguinal, Squamous Cell Carcinoma                1 (2%)                                                                       
      Lip, Squamous Cell Carcinoma                                  1 (2%)                                                          
      Pinna, Fibrosarcoma                                                        1 (2%)                                             
      Subcutaneous Tissue, Fibroma                                               1 (2%)       2 (4%)                                
      Subcutaneous Tissue, Histiocytic Sarcoma                                                1 (2%)                                
      Subcutaneous Tissue, Lipoma                                                1 (2%)                                             
      Subcutaneous Tissue, Sarcoma                     1 (2%)                                                                       
      Tail, Keratoacanthoma                                                                   1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                             Page   9                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (56)         (56)         (56)         (56)                                   
      Astrocytoma Malignant                                                                   1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Larynx                                             (56)         (56)         (56)         (56)                                   
   Lung                                               (56)         (56)         (56)         (56)                                   
      Alveolar/Bronchiolar Adenoma                                  3 (5%)      13 (23%)     11 (20%)                               
      Alveolar/Bronchiolar Adenoma, Multiple                        1 (2%)                    3 (5%)                                
      Alveolar/Bronchiolar Carcinoma                   1 (2%)       2 (4%)       1 (2%)       6 (11%)                               
      Carcinoma, Metastatic, Kidney                    1 (2%)                                                                       
      Carcinoma, Metastatic, Zymbal's Gland                         1 (2%)       1 (2%)       1 (2%)                                
      Sarcoma, Metastatic, Skin                        1 (2%)                                                                       
      Mediastinum, Alveolar/Bronchiolar Carcinoma,                                                                                  
           Metastatic, Lung                            1 (2%)                                 1 (2%)                                
      Mediastinum, Carcinoma, Metastatic, Kidney       1 (2%)                                                                       
   Nose                                               (55)         (55)         (56)         (56)                                   
      Osteoma                                          1 (2%)                                                                       
      Respiratory Epithelium, Adenoma                                                         1 (2%)                                
   Trachea                                            (56)         (56)         (56)         (56)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Zymbal's Gland                                                  (3)          (1)          (1)                                    
      Carcinoma                                                     3 (100%)     1 (100%)     1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (55)         (55)         (56)         (56)                                   
      Bilateral, Carcinoma                             1 (2%)                                                                       
   Urinary Bladder                                    (56)         (55)         (56)         (55)                                   
      Transitional Epithelium, Carcinoma               1 (2%)                                                                       
                                                                                                                                    
                                                             Page  10                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 SYSTEMIC LESIONS                                                                                                                   
   Multiple Organs                                   *(56)        *(56)        *(56)        *(56)                                   
      Histiocytic Sarcoma                                                                     1 (2%)                                
      Leukemia Mononuclear                            27 (48%)      2 (4%)       1 (2%)       1 (2%)                                
      Mesothelioma Malignant                           1 (2%)       1 (2%)       4 (7%)       2 (4%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
     *   Number of animals with any tissue examined microscopically                                                                 
                                                             Page  11                                                               
NTP Experiment-Test: 05185-03  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: 10:47:26  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            54          53          52          56                                       
     Total Primary Neoplasms                          122         107         120         132                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 50          52          49          54                                       
     Total Benign Neoplasms                            83          91         105         115                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              32          15          14          15                                       
     Total Malignant Neoplasms                         39          16          15          17                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              5           2           5           6                                       
     Total Metastatic Neoplasm                         16           3           5          17                                       
                                                                                                                                    
   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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