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TDMS Study 55301-04 Pathology Tables

NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96
Route: DOSED WATER                                                                                                Time: 15:36:01

                                                           CORE STUDY




       Facility:  TSI Mason Research

       Chemical CAS #:  110-86-1

       Lock Date:  None

       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: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        0 PPM        125 PPM      250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 

  Animals Initially in Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Natural Death                                     12           12           21           11                                     
    Accidently Killed                                  3            6            4            5                                     
    Moribund Sacrifice                                 3            2            3            5                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                32           30           22           29                                     

  Animals Examined Microscopically                    50           50           50           50                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Esophagus                                          (50)         (50)         (50)         (50)                                   
   Gallbladder                                        (37)         (40)         (33)         (34)                                   
   Intestine Large, Rectum                            (44)         (48)         (47)         (47)                                   
   Intestine Large, Cecum                             (44)         (49)         (40)         (45)                                   
      Leiomyosarcoma                                                                          1 (2%)                                
   Intestine Small, Jejunum                           (42)         (47)         (38)         (43)                                   
   Intestine Small, Ileum                             (43)         (48)         (37)         (41)                                   
      Carcinoma                                                                               1 (2%)                                
   Liver                                              (49)         (50)         (50)         (50)                                   
      Hemangioma                                                                              1 (2%)                                
      Hepatoblastoma                                   1 (2%)       2 (4%)       6 (12%)     12 (24%)                               
      Hepatoblastoma, Multiple                                                   3 (6%)       4 (8%)                                
      Hepatocellular Carcinoma                        10 (20%)     12 (24%)     19 (38%)     11 (22%)                               
      Hepatocellular Carcinoma, Multiple               3 (6%)      11 (22%)     14 (28%)     30 (60%)                               
      Hepatocellular Adenoma                          13 (27%)      5 (10%)      6 (12%)      4 (8%)                                
      Hepatocellular Adenoma, Multiple                24 (49%)     34 (68%)     37 (74%)     30 (60%)                               
      Histiocytic Sarcoma                              1 (2%)       1 (2%)                                                          
      Sarcoma, Metastatic, Skin                        1 (2%)                                                                       
   Mesentery                                          (17)         (18)         (13)         (13)                                   
      Hepatoblastoma, Metastatic, Liver                                          1 (8%)       1 (8%)                                
      Histiocytic Sarcoma                                           2 (11%)                                                         
      Lipoma                                                        1 (6%)                                                          
      Sarcoma                                                       2 (11%)                                                         
   Pancreas                                           (49)         (49)         (47)         (48)                                   
      Histiocytic Sarcoma                                           2 (4%)                                                          
      Sarcoma, Metastatic, Mesentery                                1 (2%)                                                          
   Salivary Glands                                    (50)         (50)         (49)         (50)                                   
      Schwannoma Malignant, Metastatic, Skin                        1 (2%)                                                          
   Stomach, Forestomach                               (49)         (49)         (49)         (49)                                   
      Squamous Cell Papilloma                                       1 (2%)                                                          
   Stomach, Glandular                                 (48)         (49)         (48)         (49)                                   
____________________________________________________________________________________________________________________________________

                                                             Page   2                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        0 PPM        125 PPM      250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Blood Vessel                                       (48)         (47)         (47)         (47)                                   
      Aorta, Histiocytic Sarcoma                                    1 (2%)                                                          
   Heart                                              (50)         (50)         (50)         (50)                                   
      Histiocytic Sarcoma                                           1 (2%)                                                          
      Sarcoma, Metastatic, Skin                                                  1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (49)         (50)         (48)         (50)                                   
      Carcinoma, Multiple                              1 (2%)                                                                       
      Histiocytic Sarcoma                              1 (2%)       1 (2%)                                                          
      Sarcoma, Metastatic, Mesentery                                1 (2%)                                                          
      Capsule, Adenoma                                 1 (2%)                                                                       
   Islets, Pancreatic                                 (49)         (50)         (47)         (49)                                   
      Adenoma                                          1 (2%)       2 (4%)                                                          
   Pituitary Gland                                    (47)         (44)         (42)         (46)                                   
      Pars Distalis, Adenoma                           8 (17%)      9 (20%)      6 (14%)      2 (4%)                                
   Thyroid Gland                                      (50)         (50)         (50)         (50)                                   
      Follicular Cell, Adenoma                         3 (6%)       2 (4%)       3 (6%)       3 (6%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   Peritoneum                                                                   (2)                                                 
      Hepatoblastoma, Metastatic, Liver                                          1 (50%)                                            
   Tissue NOS                                                                   (2)                                                 
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                                  1 (50%)                                            
      Hepatoblastoma, Metastatic, Liver                                          1 (50%)                                            
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Clitoral Gland                                     (47)         (48)         (48)         (45)                                   
   Ovary                                              (47)         (49)         (46)         (49)                                   
      Cystadenoma                                      4 (9%)       3 (6%)       1 (2%)                                             
      Granulosa Cell Tumor Benign                      1 (2%)                    1 (2%)                                             
      Hemangioma                                                                              1 (2%)                                
      Histiocytic Sarcoma                              1 (2%)       1 (2%)                                                          
      Sarcoma, Metastatic, Mesentery                                1 (2%)                                                          
   Oviduct                                                         (1)                                                              
      Schwannoma Malignant, Metastatic, Skin                        1 (100%)                                                        
   Uterus                                             (48)         (50)         (47)         (50)                                   
      Adenoma                                          1 (2%)                                                                       

                                                             Page   3                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        0 PPM        125 PPM      250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
GENITAL SYSTEM - cont                                                                                                               
      Histiocytic Sarcoma                                           1 (2%)                                                          
      Polyp Stromal                                    2 (4%)       1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (49)         (50)         (49)         (50)                                   
      Histiocytic Sarcoma                              1 (2%)       1 (2%)                                                          
   Lymph Node                                         (10)         (10)         (7)          (7)                                    
      Iliac, Histiocytic Sarcoma                       1 (10%)      1 (10%)                                                         
      Iliac, Rhabdomyosarcoma, Metastatic,                                                                                          
          Skeletal Muscle                                           1 (10%)                                                         
      Mediastinal, Sarcoma, Metastatic, Mesentery                   1 (10%)                                                         
      Mediastinal, Sarcoma, Metastatic, Skin           1 (10%)                                                                      
      Pancreatic, Hepatoblastoma, Metastatic, Liver                              1 (14%)                                            
      Pancreatic, Sarcoma, Metastatic, Mesentery                    1 (10%)                                                         
   Lymph Node, Mandibular                             (48)         (50)         (49)         (47)                                   
      Histiocytic Sarcoma                              2 (4%)       1 (2%)                                                          
      Sarcoma, Metastatic, Skin                                                  1 (2%)                                             
      Schwannoma Malignant, Metastatic, Skin                        1 (2%)                                                          
   Lymph Node, Mesenteric                             (48)         (47)         (43)         (45)                                   
      Hemangioma                                                                              1 (2%)                                
      Hepatoblastoma, Metastatic, Liver                                          1 (2%)       1 (2%)                                
      Histiocytic Sarcoma                              1 (2%)       2 (4%)                                                          
   Spleen                                             (49)         (50)         (48)         (49)                                   
      Histiocytic Sarcoma                              1 (2%)       1 (2%)                                                          
   Thymus                                             (45)         (44)         (46)         (39)                                   
      Alveolar/Bronchiolar Carcinoma, Metastatic,                                                                                   
           Lung                                                                  1 (2%)                                             
      Histiocytic Sarcoma                                           1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Skin                                               (49)         (50)         (50)         (50)                                   
      Squamous Cell Papilloma                          1 (2%)       1 (2%)                                                          
      Subcutaneous Tissue, Hemangioma                                            1 (2%)                                             
      Subcutaneous Tissue, Hemangiosarcoma                                       1 (2%)                                             
      Subcutaneous Tissue, Sarcoma                     2 (4%)       2 (4%)       3 (6%)       4 (8%)                                
      Subcutaneous Tissue, Schwannoma Malignant        1 (2%)       1 (2%)       1 (2%)       1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    

                                                             Page   4                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        0 PPM        125 PPM      250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Skeletal Muscle                                                 (1)          (1)          (1)                                    
      Hepatoblastoma, Metastatic, Liver                                          1 (100%)                                           
      Rhabdomyosarcoma                                              1 (100%)                                                        
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (50)         (50)         (50)         (50)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (50)         (50)         (50)         (50)                                   
      Alveolar/Bronchiolar Adenoma                     1 (2%)       3 (6%)                    3 (6%)                                
      Alveolar/Bronchiolar Adenoma, Multiple           1 (2%)                                                                       
      Alveolar/Bronchiolar Carcinoma                   2 (4%)       1 (2%)       2 (4%)       3 (6%)                                
      Carcinoma, Metastatic, Harderian Gland           1 (2%)                                                                       
      Hepatoblastoma, Metastatic, Liver                                          1 (2%)       3 (6%)                                
      Hepatocellular Carcinoma, Metastatic, Liver      2 (4%)                    6 (12%)     10 (20%)                               
      Histiocytic Sarcoma                              1 (2%)       1 (2%)                                                          
      Rhabdomyosarcoma, Metastatic, Skeletal Muscle                 1 (2%)                                                          
      Sarcoma, Metastatic, Mesentery                                1 (2%)                                                          
      Sarcoma, Metastatic, Skin                                                  2 (4%)                                             
      Schwannoma Malignant, Metastatic, Skin                        1 (2%)                                                          
      Mediastinum, Alveolar/Bronchiolar Carcinoma,                                                                                  
           Metastatic, Lung                                                      1 (2%)                                             
      Mediastinum, Sarcoma, Metastatic, Skin                                     1 (2%)                                             
      Mediastinum, Schwannoma Malignant,                                                                                            
          Metastatic, Skin                                          1 (2%)                                                          
   Nose                                               (50)         (50)         (47)         (50)                                   
      Sarcoma                                                                                 1 (2%)                                
      Sarcoma, Metastatic, Skin                        1 (2%)                                                                       
   Trachea                                            (50)         (50)         (50)         (50)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Harderian Gland                                    (1)          (1)                       (1)                                    
      Adenoma                                                       1 (100%)                                                        
      Carcinoma                                        1 (100%)                               1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    

                                                             Page   5                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        0 PPM        125 PPM      250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (49)         (50)         (49)         (49)                                   
      Histiocytic Sarcoma                              1 (2%)       1 (2%)                                                          
      Schwannoma Malignant, Metastatic, Skin                        1 (2%)                                                          
   Urinary Bladder                                    (45)         (49)         (44)         (43)                                   
      Histiocytic Sarcoma                                           1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SYSTEMIC LESIONS                                                                                                                   

   Multiple Organs                                   *(50)        *(50)        *(50)        *(50)                                   
      Histiocytic Sarcoma                              2 (4%)       2 (4%)                                                          
      Leukemia Granulocytic                                         1 (2%)                                                          
      Lymphoma Malignant                               6 (12%)      7 (14%)      4 (8%)       6 (12%)                               
      Mesothelioma Malignant                                                                  2 (4%)                                
____________________________________________________________________________________________________________________________________

                                                                                                                                    
     *   Number of animals with any tissue examined microscopically                                                                 

                                                             Page   6                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE FEMALE                        0 PPM        125 PPM      250 PPM      500 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            47          45          45          45                                       
     Total Primary Neoplasms                           90         105         108         122                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 40          41          43          36                                       
     Total Benign Neoplasms                            61          63          55          45                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              26          30          40          44                                       
     Total Malignant Neoplasms                         29          42          53          77                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              5           3          10          12                                       
     Total Metastatic Neoplasm                          6          14          21          15                                       
                                                                                                                                    
   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   7                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          0 PPM        250 PPM      500 PPM      1000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
DISPOSITION SUMMARY                                                                                                                 

  Animals Initially in Study                          50           50           50           50                                     
  Early Deaths                                                                                                                      
    Natural Death                                     11           18           11           11                                     
    Accidently Killed                                  2            1            1            3                                     
    Moribund Sacrifice                                 2            3            3            1                                     
  Survivors                                                                                                                         
    Natural Death                                                                1                                                  
    Terminal Sacrifice                                35           28           34           35                                     

  Animals Examined Microscopically                    50           50           49           50                                     
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Intestine Small, Duodenum                          (43)         (44)         (43)         (44)                                   
   Intestine Small, Jejunum                           (40)         (46)         (42)         (44)                                   
      Carcinoma                                                                               1 (2%)                                
      Histiocytic Sarcoma                                                        1 (2%)                                             
   Liver                                              (50)         (50)         (49)         (50)                                   
      Hemangioma                                                    1 (2%)                                                          
      Hemangiosarcoma                                  1 (2%)                                                                       
      Hemangiosarcoma, Multiple                                     2 (4%)                                                          
      Hepatoblastoma                                   1 (2%)      14 (28%)     16 (33%)     13 (26%)                               
      Hepatoblastoma, Multiple                         1 (2%)       4 (8%)       6 (12%)      2 (4%)                                
      Hepatocellular Carcinoma                        12 (24%)     16 (32%)     15 (31%)     22 (44%)                               
      Hepatocellular Carcinoma, Multiple               3 (6%)      19 (38%)     26 (53%)     18 (36%)                               
      Hepatocellular Adenoma                          13 (26%)     11 (22%)      5 (10%)     11 (22%)                               
      Hepatocellular Adenoma, Multiple                16 (32%)     29 (58%)     29 (59%)     28 (56%)                               
      Hepatocholangiocarcinoma, Multiple                            1 (2%)                                                          
      Histiocytic Sarcoma                              1 (2%)       2 (4%)                                                          
      Mast Cell Tumor Malignant, Metastatic, Skin                                1 (2%)                                             
      Sarcoma, Metastatic, Mesentery                                1 (2%)                                                          
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (2%)                                
   Mesentery                                          (2)          (7)          (6)          (4)                                    
      Hepatocholangiocarcinoma, Metastatic, Liver                   1 (14%)                                                         
      Histiocytic Sarcoma                                           1 (14%)                                                         
      Sarcoma                                                       1 (14%)      1 (17%)                                            
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (25%)                               
   Pancreas                                           (49)         (50)         (48)         (50)                                   
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (2%)                                
   Stomach, Forestomach                               (49)         (50)         (48)         (49)                                   
      Squamous Cell Papilloma                          1 (2%)                                                                       

                                                             Page   8                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          0 PPM        250 PPM      500 PPM      1000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - cont                                                                                                            
   Stomach, Glandular                                 (49)         (50)         (48)         (47)                                   
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (50)         (50)         (49)         (50)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (49)         (49)         (49)         (49)                                   
      Adenoma                                          1 (2%)                                 1 (2%)                                
      Sarcoma, Metastatic, Mesentery                                1 (2%)                                                          
      Capsule, Adenoma                                 2 (4%)                                                                       
      Capsule, Sarcoma, Metastatic, Mesentery                                    1 (2%)                                             
      Capsule, Squamous Cell Carcinoma, Metastatic,                                                                                 
           Uncertain Primary Site                                                             1 (2%)                                
   Adrenal Medulla                                    (48)         (48)         (49)         (49)                                   
      Pheochromocytoma Benign                                       1 (2%)                                                          
      Sarcoma, Metastatic, Mesentery                                1 (2%)                                                          
   Islets, Pancreatic                                 (49)         (50)         (48)         (50)                                   
      Adenoma                                                       1 (2%)       2 (4%)       1 (2%)                                
   Thyroid Gland                                      (49)         (50)         (49)         (50)                                   
      Follicular Cell, Adenoma                         2 (4%)       2 (4%)       1 (2%)       2 (4%)                                
      Follicular Cell, Adenoma, Multiple                                         1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   Peritoneum                                                                                (1)                                    
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (100%)                              
   Tissue NOS                                                                   (1)                                                 
      Thoracic, Hemangiosarcoma                                                  1 (100%)                                           
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Coagulating Gland                                               (1)                                                              
      Sarcoma, Metastatic, Mesentery                                1 (100%)                                                        
   Epididymis                                         (50)         (50)         (49)         (50)                                   
      Sarcoma                                                       1 (2%)                                                          
      Sarcoma, Metastatic, Mesentery                                1 (2%)       1 (2%)                                             
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (2%)                                

                                                             Page   9                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          0 PPM        250 PPM      500 PPM      1000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
GENITAL SYSTEM - cont                                                                                                               
   Preputial Gland                                    (50)         (50)         (49)         (49)                                   
      Sarcoma, Metastatic, Mesentery                                             1 (2%)                                             
   Prostate                                           (50)         (48)         (48)         (49)                                   
      Sarcoma, Metastatic, Mesentery                                             1 (2%)                                             
   Seminal Vesicle                                    (49)         (49)         (49)         (50)                                   
      Sarcoma, Metastatic, Mesentery                                1 (2%)       1 (2%)                                             
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (2%)                                
   Testes                                             (50)         (50)         (49)         (50)                                   
      Sarcoma, Metastatic, Mesentery                                1 (2%)       1 (2%)                                             
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (49)         (50)         (49)         (50)                                   
      Hemangiosarcoma                                               1 (2%)                                                          
      Hemangiosarcoma, Metastatic, Liver                            1 (2%)                                                          
      Histiocytic Sarcoma                              1 (2%)       1 (2%)                                                          
      Mast Cell Tumor Malignant, Metastatic, Skin                                1 (2%)                                             
   Lymph Node                                         (2)          (4)          (4)          (2)                                    
      Mediastinal, Hepatocholangiocarcinoma,                                                                                        
          Metastatic, Liver                                         1 (25%)                                                         
      Mediastinal, Sarcoma, Metastatic, Mesentery                   1 (25%)      1 (25%)                                            
      Mediastinal, Squamous Cell Carcinoma,                                                                                         
          Metastatic, Uncertain Primary Site                                                  1 (50%)                               
   Lymph Node, Mandibular                             (48)         (47)         (48)         (50)                                   
      Mast Cell Tumor Malignant, Metastatic, Skin                                1 (2%)                                             
      Squamous Cell Carcinoma, Metastatic, Skin        1 (2%)                                                                       
   Lymph Node, Mesenteric                             (43)         (47)         (44)         (50)                                   
      Hemangioma                                                    1 (2%)       1 (2%)                                             
      Histiocytic Sarcoma                                           1 (2%)       1 (2%)                                             
      Sarcoma, Metastatic, Mesentery                                             1 (2%)                                             
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (2%)                                
   Spleen                                             (49)         (50)         (47)         (49)                                   
      Hemangiosarcoma                                  1 (2%)       3 (6%)       1 (2%)       1 (2%)                                
      Hemangiosarcoma, Metastatic, Liver                            1 (2%)                                                          
      Histiocytic Sarcoma                                           1 (2%)                                                          
      Mast Cell Tumor Malignant, Metastatic, Skin                                1 (2%)                                             
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (2%)                                
   Thymus                                             (46)         (46)         (39)         (47)                                   
      Hepatocellular Carcinoma, Metastatic, Liver                   1 (2%)                                                          
      Sarcoma, Metastatic, Mesentery                                             1 (3%)                                             
____________________________________________________________________________________________________________________________________

                                                             Page  10                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          0 PPM        250 PPM      500 PPM      1000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Skin                                               (49)         (50)         (48)         (50)                                   
      Squamous Cell Carcinoma                          1 (2%)                                                                       
      Subcutaneous Tissue, Basal Cell Adenoma                                                 1 (2%)                                
      Subcutaneous Tissue, Hemangioma                               1 (2%)                    1 (2%)                                
      Subcutaneous Tissue, Hemangiosarcoma             1 (2%)                                                                       
      Subcutaneous Tissue, Histiocytic Sarcoma                      1 (2%)                                                          
      Subcutaneous Tissue, Mast Cell Tumor                                                                                          
          Malignant                                                              1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Skeletal Muscle                                                 (3)          (2)          (1)                                    
      Hepatoblastoma, Metastatic, Liver                             1 (33%)                                                         
      Sarcoma, Metastatic, Mesentery                                1 (33%)      1 (50%)                                            
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (100%)                              
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (50)         (50)         (49)         (50)                                   
      Histiocytic Sarcoma                                           1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Lung                                               (49)         (50)         (49)         (50)                                   
      Alveolar/Bronchiolar Adenoma                    10 (20%)      5 (10%)      7 (14%)      6 (12%)                               
      Alveolar/Bronchiolar Adenoma, Multiple           2 (4%)                    1 (2%)       2 (4%)                                
      Alveolar/Bronchiolar Carcinoma                   1 (2%)       2 (4%)       1 (2%)       1 (2%)                                
      Hemangiosarcoma, Metastatic, Liver                            1 (2%)                                                          
      Hepatoblastoma, Metastatic, Liver                             4 (8%)       7 (14%)      3 (6%)                                
      Hepatocellular Carcinoma, Metastatic, Liver      7 (14%)      7 (14%)     11 (22%)     13 (26%)                               
      Hepatocholangiocarcinoma, Metastatic, Liver                   1 (2%)                                                          
      Histiocytic Sarcoma                                           1 (2%)                                                          
      Mediastinum, Hepatocellular Carcinoma,                                                                                        
          Metastatic, Liver                                         1 (2%)                                                          
      Mediastinum, Hepatocholangiocarcinoma,                                                                                        
          Metastatic, Liver                                         1 (2%)                                                          
   Nose                                               (50)         (49)         (49)         (50)                                   
____________________________________________________________________________________________________________________________________
                                                                                                                                    

                                                             Page  11                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          0 PPM        250 PPM      500 PPM      1000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Harderian Gland                                    (5)                                    (1)                                    
      Adenoma                                          3 (60%)                                1 (100%)                              
      Carcinoma                                        2 (40%)                                                                      
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (49)         (50)         (48)         (50)                                   
      Hemangiosarcoma, Metastatic, Tissue NOS                                    1 (2%)                                             
      Histiocytic Sarcoma                                           1 (2%)                                                          
      Mast Cell Tumor Malignant, Metastatic, Skin                                1 (2%)                                             
      Sarcoma, Metastatic, Mesentery                                             1 (2%)                                             
      Renal Tubule, Adenoma                                         1 (2%)       1 (2%)                                             
   Urinary Bladder                                    (48)         (49)         (44)         (50)                                   
      Hemangioma                                                                 1 (2%)                                             
      Squamous Cell Carcinoma, Metastatic,                                                                                          
          Uncertain Primary Site                                                              1 (2%)                                
      Transitional Epithelium, Papilloma               1 (2%)                                                                       
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SYSTEMIC LESIONS                                                                                                                   

   Multiple Organs                                   *(50)        *(50)        *(49)        *(50)                                   
      Histiocytic Sarcoma                              1 (2%)       2 (4%)       1 (2%)                                             
      Lymphoma Malignant                               3 (6%)       3 (6%)       3 (6%)       1 (2%)                                
      Mesothelioma Malignant                                                     1 (2%)       1 (2%)                                
____________________________________________________________________________________________________________________________________

                                                                                                                                    
     *   Number of animals with any tissue examined microscopically                                                                 

                                                             Page  12                                                               
NTP Experiment-Test: 55301-04  INCIDENCE RATES OF NEOPLASMS BY ANATOMIC SITE (SYSTEMIC LESIONS ABRIDGED) (a)      Report: PEIRPT05
Study Type: CHRONIC                                              PYRIDINE                                         Date: 11/19/96  
Route: DOSED WATER                                                                                                Time: 15:36:01  
____________________________________________________________________________________________________________________________________
                                                                                                                                    
         B6C3F1 MICE MALE                          0 PPM        250 PPM      500 PPM      1000 PPM                                  
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
TUMOR SUMMARY                                                                                                                       
                                                                                                                                    
   Total Animals with Primary Neoplasms (b)            43          49          48          47                                       
     Total Primary Neoplasms                           79         122         122         114                                       
                                                                                                                                    
   Total Animals with Benign Neoplasms                 35          42          36          39                                       
     Total Benign Neoplasms                            51          53          49          54                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms              22          46          47          42                                       
     Total Malignant Neoplasms                         28          69          73          60                                       
                                                                                                                                    
   Total Animals with Metastatic Neoplasms              8          12          19          14                                       
     Total Metastatic Neoplasm                          8          30          35          30                                       
                                                                                                                                    
   Total Animals with Malignant Neoplasms                                                   1                                       
   Uncertain Primary Site                                                                                                           
                                                                                                                                    
   Total Animals with Neoplasms Uncertain-                                                                                          
   Benign or Malignant                                                                                                              
     Total Uncertain Neoplasms                                                                                                      
                                                                                                                                    

____________________________________________________________________________________________________________________________________
a  Number of animals examined microscopically at site and number of animals with lesion                                             
b  Primary tumors: all tumors except metastatic tumors                                                                              

                                                             Page  13                                                               
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