NEOPLASTIC DISEASES IN CHICKENS 53 



other. Histiocytic sarcomas and carcinosarcomas may also be included in this 

 group which may require microscopic examination for accurate identification. 



A nodular type of tumor found widespread over the peritoneum, usually in- 

 volving abdominal organs and associated with considerable ascites, proved to 

 be either carcinosarcoma, fibrosarcoma, or carcinoma (Plate VIII, Figure 1; 

 Plate XII, Figure 1). Satisfactory criteria for distinguishing these tumors on 

 macroscopic examination could not be established. Fibrosarcom.a proved partic- 

 ularly difficult to identify accurately on macroscopic examination. Only five 

 of the twenty-five diagnoses proved correct (20 percent), and five of the eleven 

 fibrosarcomas were recognized on macroscopic examination (45 percent). Of the 

 inaccurate tentative diagnoses, eleven proved to be lymphocytoma and the 

 remainder were principally other neoplasms of connective tissue origin. 



Leiomyomas involving the ventral ligament of the oviduct usually were prop- 

 erly recognized (Plate XII, Figure 2). Leiom\omas occurring in the wall of the 

 oviduct, in the intestine, and in other locations might be more difficult to identify 

 from macroscopic examination. 



The gross character of embryonal nephroma is quite variable and might lead 

 to incorrect interpretation (Plate X. Figures 1 and 2). However, encapsulated 

 tumors arising from the kidney or its vicinit\-, even though the base be narrow 

 or the attachment rather loose, can be reasonabh' correctly identified as embryonal 

 nephroma, particularly in the absence of lesions in other organs. No tentative 

 diagnosis of embryonal nephroma proved to be incorrect. Three of the four 

 embryonal nephromas which were not recognized as such were classed as fibro- 

 sarcoma o 1 gross examination and one was considered to represent a cystic kidne}'. 



The incorrect tentati^'e designation of neurogenic sarcoma in seven cases of 

 lymphocytoma was based largely on location of the lesions. The neurogenic 

 sarcomas were in general of a more glistening white color and of firmer con- 

 sistency. Those neurogenic sarcomas which are encapsulated should be more 

 readily recognized than those which invade and infiltrate adjacent tissues (Plate 

 I, Figures 1 and 3). 



To differentiate neoplasia from granulomatous and inflammatory reactions 

 may be difficult, particularly when necrosis occurs in the substance of a tumor. 

 Marked post-mortem changes may lead to confusion. Likewise the concomitant 

 existence of both a granulomatous process and neoplastic disease in the same 

 bird may give trouble in correctly identifying a tumor. Inflammatory and 

 neoplastic processes in the proventriculus may be particularly difficult to differen- 

 tiate. Cholangioma, cholangitis, and cirrhotic liver changes may have many 

 points of resemblance. The differentiation between lymphocytoma in the kidney 

 and chronic nephritis may occasionally be difficult, but in general the kidney in 

 chronic nephritis has a firmer texture. 



The identification of tumors is often considered a difficult problem. In many 

 laboratories engaged in the diagnosis of poultry diseases, histological examina- 

 tions are not made of all neoplasms, and instances of neoplastic disease encount- 

 ered in such laboratories are apt to be relegated to the doubtful category of tumors. 

 It would seem desirable to improve this situation and designate the type of 

 tumors observed as accurately as possible. Considerable accuracy and confi- 

 dence in identification of tumors upon macroscopic examination can be attained 

 by application of knowledge gained from a correlation of a series of diagnoses 

 tentatively based on macroscopic and checked by microscopic examination. 

 Such a study would not be impractical for most diagnostic laboratories. After 

 completion of such a series, occasional check examinations could be made to 

 maintain accurac\' and confidence. Histological examination should always be 

 resorted to in doubtful cases. 



