NEOPLASTIC DISEASES IN CHICKENS 



43 



GENERAL DISCUSSION 



Incidence 



The material studied provides some information on the incidence of tumors. 

 A number of variable factors influence statistics on this subject, and it is obvious 

 that very few factors likely to affect the rate of neoplasia can be recognized and 

 controlled in material such as that with which we were dealing. Despite these 

 limitations the data are sufficient to merit examination. 



Table 20. — Relative INCIDE^"CE of Neoplasms in Collections A, B, and C 

 Correlated with Source. 



Type of 

 Neoplasia 



A and B Combined C 



Entire Series 



Number Percent Number Percent Number Percent Number Number Percent 

 of of Birds of of Birds of of Birds of of of Total 



Cases Examined Cases Examined Cases Examined Cases Cases Neoplasms 

 (1781) (523) (2304) Found 



(384) 



Lymphocytoma 112 6.29 



Leiomyoma.... 11 .62 

 Embryonal 



nephroma. . . 13 .73 



Myelocytoma . . 14 .78 



Leukosis 14 .78 



Epithelio- 



blastoma. ... 10 .56 



Fibrosarcoma. . 12 .67 



Carcinosarcoma 2 .11 

 Neurogenic 



sarcoma. .... 3 .17 



Hemangioma... 4 .22 



Fibroma 3 .17 



Cholangioma. . . 3 .17 



Hepatoma 2 .11 



Histiocytic 



sarcoma 3 .17 



Myxoma 2 .11 



Thymoma 2 .11 



Rhabdomyoma 2 .11 

 Osteochondro- 

 sarcoma 1 .055 



Fibrochondro- 



sarcoma 



Melanoma 1 .055 



Lymphangioma 1 .055 



Mesothelioma.. 1 .055 



Teratoma 



Total 216 12.1 



The relative incidence of the different varieties of neoplasia is indicated in 

 Table 20. In addition to the numbers of different types of neoplasia found in 

 collections A, B, and C, the frequency of incidence is calculated according to the 

 source of material. Since collection C was derived from miscellaneous sources, 

 data on relative frequency were not available. In order to provide a larger sample 

 from which to obtain information on incidence as related to breed, sex, age, and 

 season, the data for collections A and B were pooled. The distribution of all 

 chickens over six weeks of age examined in the material providing collections 

 A and B is given in Table 21, with respect to breed, age, and season of necropsy. 

 Comparable data on the neoplastic diseases f round in collections A and B are 

 given in Table 22. 



Only a few varieties of neoplasia are represented in sufficient numbers to justify 

 an attempt at judging their rate of incidence in birds examined for disease. These 

 are lymphocytoma, embryonal nephroma, myelocytoma, leukosis, and fibro- 



