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TDMS Study 88070-04 Pathology Tables

NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18

                                                           CORE STUDY




       Facility:  Battelle Northwest

       Chemical CAS #:  115-11-0007

       Lock Date:  10/05/95

       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: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially in Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                13           16            6           13                                     
    Natural Death                                      5            3            5            4                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                32           31           39           33                                     
  Animals Examined Microscopically                    50           50           50           50                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Intestine Large, Colon                             (46)         (48)         (49)         (50)                                   
   Intestine Large, Cecum                             (46)         (47)         (47)         (48)                                   
   Intestine Small, Jejunum                           (46)         (47)         (46)         (47)                                   
      Carcinoma                                                     1 (2%)                                                          
   Intestine Small, Ileum                             (46)         (48)         (46)         (47)                                   
   Liver                                              (47)         (50)         (50)         (50)                                   
      Hepatoblastoma                                                1 (2%)                                                          
      Hepatoblastoma, Multiple                                      1 (2%)                                                          
      Hepatocellular Carcinoma                         4 (9%)       8 (16%)      6 (12%)      9 (18%)                               
      Hepatocellular Carcinoma, Multiple               1 (2%)                    1 (2%)       2 (4%)                                
      Hepatocellular Adenoma                          15 (32%)     18 (36%)     11 (22%)     13 (26%)                               
      Hepatocellular Adenoma, Multiple                 5 (11%)      4 (8%)       8 (16%)      7 (14%)                               
      Hepatocholangiocarcinoma                         1 (2%)                                                                       
      Histiocytic Sarcoma                              2 (4%)       4 (8%)                                                          
   Mesentery                                          (7)          (8)          (8)          (10)                                   
      Histiocytic Sarcoma                                           1 (13%)                                                         
      Lipoma                                                                     1 (13%)                                            
   Pancreas                                           (47)         (50)         (48)         (49)                                   
   Salivary Glands                                    (48)         (50)         (50)         (50)                                   
   Stomach, Forestomach                               (48)         (49)         (49)         (49)                                   
      Squamous Cell Carcinoma                                                    1 (2%)                                             
   Stomach, Glandular                                 (46)         (48)         (48)         (49)                                   
      Squamous Cell Carcinoma, Metastatic, Stomach,                                                                                 
           Forestomach                                                           1 (2%)                                             
   Tongue                                                                                    (1)                                    
      Squamous Cell Papilloma                                                                 1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   2                                                               
NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (50)         (50)         (50)         (50)                                   
      Histiocytic Sarcoma                                           1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (49)         (50)         (49)         (50)                                   
      Hepatocellular Carcinoma, Metastatic, Liver                                1 (2%)                                             
      Histiocytic Sarcoma                                           1 (2%)                                                          
      Capsule, Adenoma                                              2 (4%)                    1 (2%)                                
   Adrenal Medulla                                    (48)         (49)         (49)         (49)                                   
      Pheochromocytoma Benign                                       1 (2%)       2 (4%)       2 (4%)                                
      Bilateral, Pheochromocytoma Malignant                                                   1 (2%)                                
   Islets, Pancreatic                                 (47)         (49)         (48)         (49)                                   
      Adenoma                                          1 (2%)       1 (2%)       1 (2%)                                             
   Pituitary Gland                                    (49)         (49)         (49)         (49)                                   
      Pars Distalis, Adenoma                           8 (16%)     13 (27%)     12 (24%)     12 (24%)                               
      Pars Distalis, Carcinoma                                                   1 (2%)                                             
      Pars Intermedia, Adenoma                                                   1 (2%)                                             
   Thyroid Gland                                      (48)         (50)         (49)         (50)                                   
      Follicular Cell, Adenoma                         1 (2%)       4 (8%)       3 (6%)       1 (2%)                                
      Follicular Cell, Adenoma, Multiple                                                      1 (2%)                                
      Follicular Cell, Carcinoma                                                 1 (2%)       1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Ovary                                              (48)         (50)         (48)         (50)                                   
      Cystadenoma                                                   3 (6%)       1 (2%)       2 (4%)                                
      Granulosa Cell Tumor Benign                      1 (2%)       2 (4%)                                                          
      Granulosa-Theca Tumor Benign                                                            1 (2%)                                
      Hemangioma                                                    1 (2%)       1 (2%)                                             
      Hemangiosarcoma                                                            1 (2%)                                             
      Histiocytic Sarcoma                              2 (4%)       3 (6%)       1 (2%)                                             
      Luteoma                                                                    1 (2%)                                             
      Teratoma Benign                                  1 (2%)                                                                       
      Yolk Sac Carcinoma                               1 (2%)                                                                       
   Uterus                                             (49)         (50)         (50)         (50)                                   
      Histiocytic Sarcoma                                           2 (4%)       1 (2%)                                             
      Polyp Stromal                                    2 (4%)       1 (2%)       1 (2%)                                             
      Polyp Stromal, Multiple                          1 (2%)                                                                       
                                                             Page   3                                                               
NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (48)         (49)         (49)         (50)                                   
      Hemangiosarcoma                                  1 (2%)                                                                       
      Histiocytic Sarcoma                                           2 (4%)                                                          
   Lymph Node                                         (7)          (2)          (5)          (4)                                    
      Iliac, Histiocytic Sarcoma                       1 (14%)      1 (50%)                                                         
      Inguinal, Hemangiosarcoma                                                  1 (20%)                                            
      Renal, Histiocytic Sarcoma                       1 (14%)      2 (100%)                                                        
   Lymph Node, Bronchial                              (38)         (33)         (44)         (44)                                   
      Histiocytic Sarcoma                                           1 (3%)                                                          
   Lymph Node, Mandibular                             (41)         (42)         (44)         (38)                                   
      Histiocytic Sarcoma                                           2 (5%)                                                          
   Lymph Node, Mesenteric                             (46)         (48)         (47)         (49)                                   
      Histiocytic Sarcoma                              2 (4%)       3 (6%)                                                          
   Lymph Node, Mediastinal                            (38)         (42)         (36)         (42)                                   
      Histiocytic Sarcoma                              1 (3%)       2 (5%)                                                          
   Spleen                                             (49)         (50)         (50)         (50)                                   
      Hemangiosarcoma                                  3 (6%)                                 1 (2%)                                
      Hepatocholangiocarcinoma, Metastatic, Liver      1 (2%)                                                                       
      Histiocytic Sarcoma                              1 (2%)       2 (4%)                                                          
   Thymus                                             (47)         (44)         (48)         (46)                                   
      Histiocytic Sarcoma                              1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (48)         (49)         (49)         (50)                                   
      Carcinoma                                        2 (4%)                    2 (4%)                                             
   Skin                                               (49)         (50)         (49)         (50)                                   
      Subcutaneous Tissue, Fibrosarcoma                             2 (4%)       1 (2%)       1 (2%)                                
      Subcutaneous Tissue, Fibrous Histiocytoma                                                                                     
          Malignant                                                 1 (2%)                                                          
      Subcutaneous Tissue, Hemangiosarcoma                          1 (2%)       1 (2%)                                             
      Subcutaneous Tissue, Sarcoma                     2 (4%)       2 (4%)                    2 (4%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   4                                                               
NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (49)         (50)         (50)         (50)                                   
      Astrocytoma Benign                               1 (2%)                                                                       
      Carcinoma, Metastatic, Pituitary Gland                                     1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (49)         (50)         (50)         (50)                                   
      Alveolar/Bronchiolar Adenoma                     2 (4%)       2 (4%)       2 (4%)       2 (4%)                                
      Alveolar/Bronchiolar Carcinoma                   4 (8%)       2 (4%)       2 (4%)       1 (2%)                                
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                     1 (2%)                                                          
      Carcinoma, Metastatic, Mammary Gland             1 (2%)                                                                       
      Hepatoblastoma, Metastatic, Liver                             1 (2%)                                                          
      Hepatocellular Carcinoma, Metastatic, Liver      1 (2%)       4 (8%)       2 (4%)       1 (2%)                                
      Histiocytic Sarcoma                              2 (4%)       4 (8%)                                                          
      Pheochromocytoma Malignant, Metastatic,                                                                                       
          Adrenal Medulla                                                                     1 (2%)                                
      Sarcoma, Metastatic, Skin                                     1 (2%)                                                          
   Nose                                               (47)         (50)         (49)         (50)                                   
   Pleura                                                          (1)                                                              
      Hepatoblastoma, Metastatic, Liver                             1 (100%)                                                        
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Harderian Gland                                    (2)          (2)          (1)          (2)                                    
      Adenoma                                          1 (50%)      1 (50%)      1 (100%)     1 (50%)                               
      Carcinoma                                                     1 (50%)                   1 (50%)                               
      Bilateral, Carcinoma                             1 (50%)                                                                      
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (49)         (50)         (49)         (50)                                   
      Histiocytic Sarcoma                                           3 (6%)                                                          
   Urinary Bladder                                    (45)         (49)         (49)         (50)                                   
      Histiocytic Sarcoma                                           1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SYSTEMIC LESIONS                                                                                                                   
   Multiple Organs                                   *(50)        *(50)        *(50)        *(50)                                   
      Histiocytic Sarcoma                              2 (4%)       4 (8%)       2 (4%)                                             
      Lymphoma Malignant                              16 (32%)      9 (18%)     17 (34%)     19 (38%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
     *   Number of animals with any tissue examined microscopically                                                                 
                                                             Page   5                                                               
NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            43          45          44          44                                       
     Total Primary Neoplasms                           77          86          83          82                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 29          35          33          32                                       
     Total Benign Neoplasms                            39          53          46          44                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              29          29          30          31                                       
     Total Malignant Neoplasms                         38          33          37          38                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              3           7           4           2                                       
     Total Metastatic Neoplasm                          3           8           5           2                                       
                                                                                                                                    
   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   6                                                               
NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially in Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Natural Death                                      6            9            3            9                                     
    Moribund Sacrifice                                16            9           20           13                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                28           32           27           28                                     
  Animals Examined Microscopically                    50           50           50           50                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Gallbladder                                        (46)         (40)         (45)         (34)                                   
   Intestine Large, Cecum                             (47)         (45)         (49)         (42)                                   
      Leiomyoma                                                                               1 (2%)                                
   Intestine Small, Duodenum                          (46)         (45)         (48)         (42)                                   
      Histiocytic Sarcoma                              1 (2%)                                                                       
   Intestine Small, Jejunum                           (45)         (43)         (48)         (43)                                   
      Carcinoma                                                     1 (2%)                    1 (2%)                                
   Intestine Small, Ileum                             (46)         (43)         (48)         (42)                                   
   Liver                                              (50)         (50)         (50)         (49)                                   
      Hemangiosarcoma                                  1 (2%)                    2 (4%)       2 (4%)                                
      Hepatoblastoma                                                             1 (2%)                                             
      Hepatocellular Carcinoma                        12 (24%)     12 (24%)     10 (20%)      7 (14%)                               
      Hepatocellular Carcinoma, Multiple               1 (2%)       1 (2%)       4 (8%)       7 (14%)                               
      Hepatocellular Adenoma                          15 (30%)     20 (40%)     13 (26%)     10 (20%)                               
      Hepatocellular Adenoma, Multiple                 5 (10%)      4 (8%)       5 (10%)      7 (14%)                               
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Pancreas                                           (50)         (48)         (50)         (47)                                   
   Salivary Glands                                    (50)         (49)         (50)         (50)                                   
   Stomach, Forestomach                               (50)         (49)         (50)         (48)                                   
      Squamous Cell Papilloma                          1 (2%)                                                                       
   Tooth                                              (7)          (14)         (9)          (16)                                   
      Odontoma                                         1 (14%)      3 (21%)      2 (22%)      2 (13%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (50)         (50)         (50)         (50)                                   
      Hemangiosarcoma                                                                         1 (2%)                                
      Pheochromocytoma Malignant, Metastatic,                                                                                       
          Adrenal Medulla                                           1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   7                                                               
NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (49)         (49)         (50)         (49)                                   
      Adenoma                                          1 (2%)       1 (2%)       1 (2%)                                             
      Capsule, Adenoma                                 1 (2%)       2 (4%)                    3 (6%)                                
   Adrenal Medulla                                    (49)         (49)         (50)         (49)                                   
      Pheochromocytoma Malignant                                    1 (2%)                                                          
      Pheochromocytoma Benign                                       1 (2%)       1 (2%)       2 (4%)                                
   Islets, Pancreatic                                 (50)         (48)         (50)         (48)                                   
      Adenoma                                                       1 (2%)                                                          
   Pituitary Gland                                    (50)         (48)         (49)         (48)                                   
      Pars Intermedia, Adenoma                                                                1 (2%)                                
   Thyroid Gland                                      (50)         (50)         (50)         (49)                                   
      Follicular Cell, Adenoma                                                   1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Epididymis                                         (50)         (50)         (50)         (50)                                   
   Prostate                                           (48)         (46)         (47)         (48)                                   
   Seminal Vesicle                                    (49)         (47)         (50)         (47)                                   
   Testes                                             (50)         (50)         (50)         (50)                                   
      Interstitial Cell, Adenoma                                                 1 (2%)       1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (50)         (49)         (50)         (49)                                   
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Lymph Node                                         (4)          (3)          (7)          (1)                                    
      Renal, Histiocytic Sarcoma                       1 (25%)                                                                      
   Lymph Node, Bronchial                              (30)         (33)         (32)         (32)                                   
      Pheochromocytoma Malignant, Metastatic,                                                                                       
          Adrenal Medulla                                           1 (3%)                                                          
   Lymph Node, Mandibular                             (34)         (29)         (33)         (35)                                   
   Lymph Node, Mesenteric                             (48)         (49)         (48)         (49)                                   
      Histiocytic Sarcoma                              1 (2%)                    1 (2%)                                             
   Lymph Node, Mediastinal                            (37)         (38)         (36)         (31)                                   
      Histiocytic Sarcoma                                                        1 (3%)                                             
      Pheochromocytoma Malignant, Metastatic,                                                                                       
          Adrenal Medulla                                           1 (3%)                                                          
   Spleen                                             (50)         (49)         (50)         (48)                                   
      Hemangiosarcoma                                               1 (2%)                    1 (2%)                                
                                                             Page   8                                                               
NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - cont                                                                                                         
      Histiocytic Sarcoma                              1 (2%)                    1 (2%)       1 (2%)                                
   Thymus                                             (41)         (42)         (38)         (41)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Skin                                               (49)         (50)         (50)         (50)                                   
      Subcutaneous Tissue, Hemangioma                                            1 (2%)                                             
      Subcutaneous Tissue, Sarcoma                                               1 (2%)       1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (50)         (50)         (50)         (50)                                   
      Alveolar/Bronchiolar Adenoma                     9 (18%)      5 (10%)      5 (10%)      3 (6%)                                
      Alveolar/Bronchiolar Adenoma, Multiple           3 (6%)       2 (4%)                                                          
      Alveolar/Bronchiolar Carcinoma                   6 (12%)      5 (10%)      4 (8%)       3 (6%)                                
      Alveolar/Bronchiolar Carcinoma, Multiple                      1 (2%)                    3 (6%)                                
      Hepatocellular Carcinoma, Metastatic, Liver      4 (8%)       4 (8%)       2 (4%)       3 (6%)                                
      Histiocytic Sarcoma                                                        1 (2%)                                             
      Pheochromocytoma Malignant, Metastatic,                                                                                       
          Adrenal Medulla                                           1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Harderian Gland                                    (4)          (4)          (4)          (4)                                    
      Adenoma                                          2 (50%)      3 (75%)      4 (100%)     2 (50%)                               
      Carcinoma                                        1 (25%)                                2 (50%)                               
      Bilateral, Adenoma                               1 (25%)                                                                      
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   9                                                               
NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (50)         (49)         (50)         (50)                                   
      Hepatocellular Carcinoma, Metastatic, Liver                   1 (2%)                                                          
      Histiocytic Sarcoma                                                        1 (2%)                                             
      Pheochromocytoma Malignant, Metastatic,                                                                                       
          Adrenal Medulla                                           1 (2%)                                                          
      Renal Tubule, Adenoma                            1 (2%)                    2 (4%)                                             
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SYSTEMIC LESIONS                                                                                                                   
   Multiple Organs                                   *(50)        *(50)        *(50)        *(50)                                   
      Histiocytic Sarcoma                              1 (2%)                    1 (2%)       1 (2%)                                
      Lymphoma Malignant                               4 (8%)       2 (4%)       5 (10%)      5 (10%)                               
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     *   Number of animals with any tissue examined microscopically                                                                 
                                                             Page  10                                                               
NTP Experiment-Test: 88070-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/20/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 12:23:18  
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         B6C3F1 MICE MALE                          CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
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TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            41          41          36          38                                       
     Total Primary Neoplasms                           66          66          64          66                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 30          32          27          23                                       
     Total Benign Neoplasms                            40          42          36          32                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              21          19          23          23                                       
     Total Malignant Neoplasms                         26          24          28          34                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              4           5           2           3                                       
     Total Metastatic Neoplasm                          4          10           2           3                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms                                                                                           
   Uncertain Primary Site                                                                                                           
                                                                                                                                    
   Total Animals with Neoplasms Uncertain-                                                                                          
   Benign or Malignant                                                                                                              
     Total Uncertain Neoplasms                                                                                                      
                                                                                                                                    
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a  Number of animals examined microscopically at site and number of animals with lesion                                             
b  Primary tumors: all tumors except metastatic tumors                                                                              
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