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TDMS Study 88070-03 Pathology Tables

NTP Experiment-Test: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48

                                                           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: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially in Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                21           25           15           23                                     
    Natural Death                                      6            5            2            5                                     
    Accidently Killed                                               1                                                               
  Survivors                                                                                                                         
    Terminal Sacrifice                                23           19           33           22                                     
  Animals Examined Microscopically                    50           50           50           50                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Intestine Large, Colon                             (49)         (50)         (49)         (49)                                   
   Intestine Large, Rectum                            (47)         (47)         (47)         (48)                                   
      Polyp Adenomatous                                1 (2%)                                                                       
   Intestine Large, Cecum                             (48)         (49)         (48)         (49)                                   
   Intestine Small, Duodenum                          (49)         (50)         (48)         (48)                                   
   Intestine Small, Jejunum                           (47)         (47)         (48)         (47)                                   
      Leiomyosarcoma                                                             1 (2%)                                             
   Intestine Small, Ileum                             (46)         (47)         (48)         (47)                                   
   Liver                                              (50)         (50)         (50)         (49)                                   
      Carcinoma, Metastatic, Thyroid Gland                          1 (2%)                                                          
      Hepatocellular Carcinoma                                                                1 (2%)                                
   Mesentery                                          (8)          (10)         (12)         (7)                                    
   Oral Mucosa                                                                               (1)                                    
      Pharyngeal, Squamous Cell Papilloma                                                     1 (100%)                              
   Pancreas                                           (50)         (50)         (49)         (49)                                   
   Salivary Glands                                    (50)         (50)         (50)         (50)                                   
   Stomach, Glandular                                 (50)         (50)         (50)         (49)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (50)         (50)         (49)         (50)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (50)         (50)         (49)         (49)                                   
      Adenoma                                          1 (2%)       1 (2%)       1 (2%)       1 (2%)                                
   Adrenal Medulla                                    (50)         (50)         (49)         (49)                                   
      Pheochromocytoma Complex                         1 (2%)                                                                       
      Pheochromocytoma Benign                          3 (6%)       3 (6%)       9 (18%)      4 (8%)                                
      Bilateral, Pheochromocytoma Benign                                         1 (2%)                                             
                                                             Page   2                                                               
NTP Experiment-Test: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ENDOCRINE SYSTEM - cont                                                                                                             
   Islets, Pancreatic                                 (50)         (50)         (49)         (49)                                   
      Adenoma                                          1 (2%)                                                                       
   Pituitary Gland                                    (50)         (49)         (50)         (49)                                   
      Pars Distalis, Adenoma                          39 (78%)     33 (67%)     37 (74%)     36 (73%)                               
   Thyroid Gland                                      (50)         (50)         (49)         (49)                                   
      C-Cell, Adenoma                                  7 (14%)      6 (12%)      3 (6%)       5 (10%)                               
      C-Cell, Carcinoma                                2 (4%)       3 (6%)       6 (12%)      2 (4%)                                
      Follicular Cell, Carcinoma                       1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Clitoral Gland                                     (50)         (49)         (47)         (48)                                   
      Adenoma                                          3 (6%)       3 (6%)       6 (13%)                                            
      Carcinoma                                                                  5 (11%)      1 (2%)                                
      Bilateral, Carcinoma                             1 (2%)                                                                       
   Ovary                                              (50)         (50)         (50)         (50)                                   
      Granulosa Cell Tumor Malignant                                                          1 (2%)                                
   Uterus                                             (50)         (50)         (50)         (50)                                   
      Polyp Stromal                                    7 (14%)      9 (18%)      7 (14%)      4 (8%)                                
      Polyp Stromal, Multiple                          1 (2%)                    1 (2%)       1 (2%)                                
   Vagina                                             (1)          (1)                       (1)                                    
      Polyp                                            1 (100%)                                                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (50)         (50)         (49)         (49)                                   
   Lymph Node                                         (6)          (3)          (3)          (2)                                    
      Deep Cervical, Carcinoma, Metastatic,                                                                                         
          Thyroid Gland                                                                       1 (50%)                               
      Renal, Sarcoma                                   1 (17%)                                                                      
   Lymph Node, Bronchial                              (36)         (31)         (36)         (27)                                   
   Lymph Node, Mandibular                             (44)         (46)         (47)         (47)                                   
   Lymph Node, Mesenteric                             (50)         (50)         (49)         (49)                                   
   Lymph Node, Mediastinal                            (42)         (45)         (39)         (45)                                   
      Plasma Cell Tumor Malignant                      1 (2%)                                                                       
   Spleen                                             (50)         (50)         (49)         (50)                                   
      Hemangiosarcoma                                                                         1 (2%)                                
   Thymus                                             (48)         (47)         (45)         (41)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   3                                                               
NTP Experiment-Test: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (50)         (50)         (50)         (50)                                   
      Adenoma                                          1 (2%)       1 (2%)       1 (2%)                                             
      Carcinoma                                        2 (4%)       2 (4%)       4 (8%)       4 (8%)                                
      Fibroadenoma                                    16 (32%)     14 (28%)     24 (48%)     22 (44%)                               
      Fibroadenoma, Multiple                           6 (12%)      5 (10%)      6 (12%)      5 (10%)                               
   Skin                                               (50)         (50)         (50)         (50)                                   
      Keratoacanthoma                                  1 (2%)                    1 (2%)                                             
      Squamous Cell Papilloma                                                    1 (2%)                                             
      Subcutaneous Tissue, Fibroma                     1 (2%)                    1 (2%)                                             
      Subcutaneous Tissue, Fibrosarcoma                             1 (2%)                                                          
      Subcutaneous Tissue, Fibrous Histiocytoma                                                                                     
          Malignant                                    1 (2%)                                                                       
      Subcutaneous Tissue, Hemangioma                  1 (2%)                                                                       
      Subcutaneous Tissue, Melanoma Malignant                                    1 (2%)                                             
      Subcutaneous Tissue, Sarcoma                     1 (2%)       2 (4%)                                                          
      Subcutaneous Tissue, Schwannoma Malignant                     1 (2%)                                                          
      Subcutaneous Tissue, Pinna, Melanoma                                                                                          
          Malignant                                    1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (50)         (50)         (50)         (50)                                   
      Osteosarcoma                                     1 (2%)                                                                       
      Sarcoma                                          1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (50)         (50)         (50)         (50)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (50)         (50)         (50)         (50)                                   
      Adenoma                                                       1 (2%)                                                          
      Alveolar/Bronchiolar Adenoma                     2 (4%)                                                                       
      Carcinoma, Metastatic, Mammary Gland             1 (2%)                                                                       
      Carcinoma, Metastatic, Thyroid Gland                                       2 (4%)       1 (2%)                                
      Fibrosarcoma, Metastatic, Skin                                1 (2%)                                                          
      Plasma Cell Tumor Malignant, Metastatic,                                                                                      
           Lymph Node, Mediastinal                     1 (2%)                                                                       
      Mediastinum, Plasma Cell Tumor Malignant,                                                                                     
           Metastatic, Lymph Node, Mediastinal         1 (2%)                                                                       
   Nose                                               (50)         (50)         (50)         (49)                                   
____________________________________________________________________________________________________________________________________
                                                             Page   4                                                               
NTP Experiment-Test: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Zymbal's Gland                                                               (1)                                                 
      Carcinoma                                                                  1 (100%)                                           
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (50)         (50)         (49)         (49)                                   
      Lipoma                                                                                  1 (2%)                                
      Stromal Nephroma                                              1 (2%)                                                          
      Renal Tubule, Carcinoma                          1 (2%)                                                                       
   Urinary Bladder                                    (50)         (49)         (49)         (49)                                   
      Transitional Epithelium, Papilloma                                         1 (2%)                                             
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SYSTEMIC LESIONS                                                                                                                   
   Multiple Organs                                   *(50)        *(50)        *(50)        *(50)                                   
      Leukemia Mononuclear                            18 (36%)     16 (32%)     22 (44%)     17 (34%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
     *   Number of animals with any tissue examined microscopically                                                                 
                                                             Page   5                                                               
NTP Experiment-Test: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS FEMALE                   CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            50          48          49          48                                       
     Total Primary Neoplasms                          125         102         140         107                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 42          45          48          46                                       
     Total Benign Neoplasms                            92          76         100          80                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              30          24          30          25                                       
     Total Malignant Neoplasms                         33          26          40          27                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              2           2           2           1                                       
     Total Metastatic Neoplasm                          3           2           2           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: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially in Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                39           40           37           41                                     
    Natural Death                                      4            5            7            1                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                 7            5            6            8                                     
  Animals Examined Microscopically                    50           50           50           50                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Intestine Large, Colon                             (49)         (48)         (48)         (49)                                   
   Intestine Large, Rectum                            (47)         (49)         (49)         (49)                                   
      Polyp Adenomatous                                1 (2%)                                                                       
   Intestine Large, Cecum                             (48)         (47)         (49)         (49)                                   
   Intestine Small, Jejunum                           (47)         (46)         (47)         (49)                                   
      Carcinoma                                        1 (2%)                    1 (2%)                                             
      Hemangiosarcoma                                                            1 (2%)                                             
   Intestine Small, Ileum                             (47)         (46)         (47)         (49)                                   
      Leiomyosarcoma                                                                          1 (2%)                                
   Liver                                              (50)         (50)         (50)         (50)                                   
      Histiocytic Sarcoma                              1 (2%)                    2 (4%)                                             
      Osteosarcoma, Metastatic, Bone                   1 (2%)                                                                       
   Mesentery                                          (15)         (10)         (8)          (11)                                   
      Liposarcoma                                                   1 (10%)                                                         
   Oral Mucosa                                                                  (1)                                                 
      Pharyngeal, Squamous Cell Papilloma                                        1 (100%)                                           
   Pancreas                                           (50)         (50)         (50)         (50)                                   
      Adenoma                                          2 (4%)       1 (2%)                                                          
   Salivary Glands                                    (50)         (50)         (50)         (50)                                   
   Stomach, Forestomach                               (50)         (50)         (50)         (50)                                   
   Stomach, Glandular                                 (50)         (49)         (50)         (50)                                   
   Tongue                                             (1)                                    (1)                                    
      Hemangiosarcoma                                                                         1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (50)         (50)         (50)         (50)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   7                                                               
NTP Experiment-Test: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (50)         (49)         (50)         (50)                                   
      Adenoma                                          1 (2%)                                 1 (2%)                                
      Osteosarcoma, Metastatic, Bone                   1 (2%)                                                                       
   Adrenal Medulla                                    (50)         (49)         (50)         (50)                                   
      Pheochromocytoma Malignant                                    1 (2%)       1 (2%)       2 (4%)                                
      Pheochromocytoma Benign                         13 (26%)      7 (14%)      8 (16%)     11 (22%)                               
      Bilateral, Pheochromocytoma Malignant                                                   1 (2%)                                
      Bilateral, Pheochromocytoma Benign              10 (20%)     11 (22%)      8 (16%)     12 (24%)                               
   Islets, Pancreatic                                 (50)         (49)         (50)         (50)                                   
      Adenoma                                          4 (8%)                    1 (2%)       4 (8%)                                
      Carcinoma                                        4 (8%)       2 (4%)       1 (2%)       4 (8%)                                
   Pituitary Gland                                    (50)         (49)         (50)         (49)                                   
      Pars Distalis, Adenoma                          43 (86%)     40 (82%)     40 (80%)     41 (84%)                               
   Thyroid Gland                                      (48)         (48)         (48)         (50)                                   
      C-Cell, Adenoma                                  5 (10%)      4 (8%)       5 (10%)      7 (14%)                               
      C-Cell, Carcinoma                                                          2 (4%)       1 (2%)                                
      Follicular Cell, Carcinoma                       1 (2%)                                 5 (10%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Epididymis                                         (50)         (50)         (50)         (50)                                   
   Preputial Gland                                    (50)         (50)         (49)         (50)                                   
      Adenoma                                          4 (8%)       2 (4%)       2 (4%)       1 (2%)                                
      Carcinoma                                        1 (2%)       2 (4%)       2 (4%)       3 (6%)                                
      Bilateral, Carcinoma                                          1 (2%)                                                          
   Prostate                                           (50)         (49)         (50)         (50)                                   
      Adenoma                                                                                 1 (2%)                                
   Seminal Vesicle                                    (50)         (47)         (50)         (50)                                   
   Testes                                             (50)         (50)         (50)         (50)                                   
      Bilateral, Interstitial Cell, Adenoma           13 (26%)     14 (28%)     17 (34%)     14 (28%)                               
      Interstitial Cell, Adenoma                      10 (20%)     14 (28%)     12 (24%)     11 (22%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (50)         (48)         (50)         (50)                                   
      Histiocytic Sarcoma                                                        2 (4%)                                             
   Lymph Node                                         (4)          (11)         (10)         (10)                                   
      Histiocytic Sarcoma                              1 (25%)                   1 (10%)                                            
      Iliac, Osteosarcoma, Metastatic, Bone            1 (25%)                                                                      
                                                             Page   8                                                               
NTP Experiment-Test: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - cont                                                                                                         
      Pancreatic, Histiocytic Sarcoma                                            1 (10%)                                            
   Lymph Node, Bronchial                              (30)         (41)         (35)         (45)                                   
      Histiocytic Sarcoma                              1 (3%)                    2 (6%)                                             
   Lymph Node, Mandibular                             (47)         (47)         (49)         (49)                                   
   Lymph Node, Mesenteric                             (50)         (50)         (49)         (50)                                   
   Lymph Node, Mediastinal                            (46)         (42)         (44)         (45)                                   
      Carcinoma, Metastatic, Thyroid Gland                                                    1 (2%)                                
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Spleen                                             (50)         (49)         (50)         (50)                                   
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Thymus                                             (40)         (42)         (38)         (42)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (41)         (41)         (40)         (44)                                   
      Carcinoma                                                     1 (2%)                                                          
      Carcinoma, Multiple                              1 (2%)                                                                       
      Fibroadenoma                                     1 (2%)                    1 (3%)       1 (2%)                                
   Skin                                               (50)         (50)         (50)         (50)                                   
      Basal Cell Adenoma                                                                      2 (4%)                                
      Basal Cell Carcinoma                                          2 (4%)                                                          
      Keratoacanthoma                                  3 (6%)       4 (8%)       2 (4%)       4 (8%)                                
      Squamous Cell Papilloma                                       1 (2%)       2 (4%)       1 (2%)                                
      Sebaceous Gland, Adenoma                                      2 (4%)       1 (2%)                                             
      Subcutaneous Tissue, Fibroma                     1 (2%)                    2 (4%)                                             
      Subcutaneous Tissue, Histiocytic Sarcoma                                   1 (2%)                                             
      Subcutaneous Tissue, Lipoma                      1 (2%)                                                                       
      Subcutaneous Tissue, Rhabdomyosarcoma                                                   1 (2%)                                
      Subcutaneous Tissue, Sarcoma                     1 (2%)                                                                       
      Subcutaneous Tissue, Schwannoma Benign           1 (2%)                                                                       
      Subcutaneous Tissue, Schwannoma Malignant                     1 (2%)                                                          
      Subcutaneous Tissue, Pinna, Melanoma                                                                                          
          Malignant                                                 1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (50)         (50)         (50)         (50)                                   
      Osteosarcoma                                     1 (2%)       1 (2%)                                                          
   Skeletal Muscle                                    (1)                       (1)          (1)                                    
      Histiocytic Sarcoma                                                        1 (100%)                                           
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                             Page   9                                                               
NTP Experiment-Test: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (50)         (50)         (50)         (50)                                   
      Astrocytoma Malignant                            1 (2%)                                                                       
      Histiocytic Sarcoma                                                        1 (2%)                                             
      Oligodendroglioma Malignant                      1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (50)         (50)         (50)         (50)                                   
      Alveolar/Bronchiolar Adenoma                     2 (4%)       2 (4%)       2 (4%)                                             
      Alveolar/Bronchiolar Carcinoma                                2 (4%)       1 (2%)       1 (2%)                                
      Carcinoma, Metastatic, Thyroid Gland                                                    1 (2%)                                
      Histiocytic Sarcoma                              1 (2%)                    2 (4%)                                             
      Osteosarcoma, Metastatic, Bone                   1 (2%)                                                                       
      Mediastinum, Alveolar/Bronchiolar Carcinoma,                                                                                  
           Metastatic, Lung                                         1 (2%)                                                          
   Nose                                               (49)         (49)         (50)         (49)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                (3)                       (4)                                                 
   Zymbal's Gland                                                  (2)          (1)                                                 
      Carcinoma                                                     2 (100%)     1 (100%)                                           
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (50)         (50)         (50)         (50)                                   
      Histiocytic Sarcoma                                                        1 (2%)                                             
      Stromal Nephroma                                 1 (2%)                                 1 (2%)                                
      Renal Tubule, Adenoma                            2 (4%)       1 (2%)                    2 (4%)                                
      Renal Tubule, Carcinoma                                                    2 (4%)                                             
   Urinary Bladder                                    (50)         (49)         (50)         (50)                                   
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 SYSTEMIC LESIONS                                                                                                                   
   Multiple Organs                                   *(50)        *(50)        *(50)        *(50)                                   
      Histiocytic Sarcoma                              1 (2%)                    2 (4%)                                             
      Leukemia Mononuclear                            21 (42%)     21 (42%)     20 (40%)     31 (62%)                               
      Mesothelioma Malignant                           3 (6%)       2 (4%)                                                          
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     *   Number of animals with any tissue examined microscopically                                                                 
                                                             Page  10                                                               
NTP Experiment-Test: 88070-03  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                             ISOBUTENE                                         Date: 06/11/97  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:30:48  
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         FISCHER 344 RATS MALE                     CONTROL      500 PPM      2000 PPM     8000 PPM                                  
                                                                                                                                    
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TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            50          48          49          50                                       
     Total Primary Neoplasms                          155         143         138         165                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 48          46          49          49                                       
     Total Benign Neoplasms                           117         103         104         113                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              31          33          28          40                                       
     Total Malignant Neoplasms                         38          40          34          52                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              1           1                       1                                       
     Total Metastatic Neoplasm                          4           1                       2                                       
                                                                                                                                    
   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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