NEOPLASTIC DISEASES IX CHICKENS 37 



istic fibrillary structure of the cytoplasm which tended to fray at the ends so that 

 the extreme ends of the cells were indistinct. Cells in the more compact areas 

 lacked the fibrillary character of the cytoplasm. Man\- of the tumor cells were 

 grouped in small parallel bundles, and oftentimes were noted to be concentrically 

 arranged about an atrophic bundle of muscle fibers. Numerous giant cells were 

 scattered about. These were not the usual form of giant cell noted in the reaction 

 to a foreign body. Instead the multiple nuclei were similar to those of the elon- 

 gate tumor cells and the cytoplasm had the fine fibrillar\- structure noted also 

 in the other tumor cells. These cells appear to be similar to the Plasmodium t},pe 

 of giant cell described in some cases of rhabdomyoma found in the human (Rakov 

 27). Section of the tumor in the wall of the intestine revealed it to be composed of 

 cells similar to those in the more compact part of the muscle tumor. They tended 

 to arrange themselves in a s\'ncitium with anastomosing cell processes. At the 

 edge of the tumor they seemed to join and blend themselves with the musculature 

 of the wall of the intestine, a considerable portion of which they actualh' re- 

 placed. \'an Geison's preparations were made of both tumors and a definite 

 reaction of the tumor cells could not be obtained to identify them as of muscular 

 origin. No striations could be identified in the ce'ls of either tumor. 



The diagnosis of these two cases as rhabdomyoma requires some comment. 

 Tumors derived from muscle tissue are commxnly grouped under the term m,\-o- 

 blastoma in a simple classification of tumors. The group is further subdivided 

 into leiomyoma for those tumors derived from smooth muscle tissue and rhab- 

 domyoma for those tumors derived from \oluntary or striated muscle tissue. 

 It is generally recognized that longitudinal and cross striations are a character- 

 istic of voluntary muscle and their presence in tumor cells derived from muscle 

 provides a simple, easy means of diagnosing a rhabdomyoma. These cannot 

 alwa>s be demonstrated; for example, in 17 malignant rhabdomyoblastomas 

 of man studied h\ Rakov (27) cress striation of the cells cculd not be dem.on- 

 strated in 9. Cappell and Montgomery (1) discuss this difficulty and suggest 

 that tumors derived from striated muscle be classified as rhabdomyoma when 

 cross striations can be demonstrated and as myoblastoma when they cannot 

 be shown. This conception would not permit classification of leiomyomas under 

 myoblastoma as is commonly done. 



The two cases of tumor described above seem quite clearly to have originated 

 from voluntary- muscle tissue. In one case the morphology of the cells and their 

 staining reaction were characteristic. In the other case the txpical staining 

 reaction could net be demonstrated, >et the morphology of the ribbonlike cells, 

 the fibrillary appearance of the cytoplasm, and polymorphism were very similar to 

 that described in rhabdom\oma found in man. Both cases might be considered 

 simply as myoblastomas; > et in view of their probable derivation from striated 

 muscle, the term rhabdomyoma is applied to conform to the more simple classi- 

 fication of tumors. 



Mesothelioma 



One case of the series was considered a mesothelioma. 



1. Case T 157. This was an active, 9-month-old pullet whose only symptom, 

 of disease was distension of the abdomen. The bird was killed for necropsy. 

 Approximately 700 ml. of green-tinted yellow fluid was responsible for the ab- 

 dominal distension. Two tumor masses were found in the abdomen. The smaller 

 mass was situated en the serosa of the posterio-ventral aspect of the abdomen and 

 attached by a stalk to a larger mass which in turn was connected by another 

 stalk to the body wall in the vicinity of the ovary. Both stalks consisted prin- 

 cipally of blood vessels. The larger tumor measured 5.5 X 4 X 3 cm. and weighed 

 37 grams. The smaller tumor weighed 12 grams. Both tumors were vascular and 

 gray-white in color. They were irregular in shape, relatively soft, and contained 

 small areas of necrosis. A few small cysts filled with clear fluid were noted in the 

 smaller tumor, to which were also attached some pendulous cysts filled with 

 organized blood clots. The visceral serosa was somewhat thickened and the 



