Sarcoma Occurring in a Guinea-pig. 27 



many large areas of necrosis in which practically all cellular 

 structure is lost. There is evidence of an unsuccessful attempt at 

 encapsulation, but the tumor has invaded the connective tissue 

 of the capsule as well as the adjacent areolar tissue. 



The majority of the cells of the tumor resemble lymphocytes 

 in size and in appearance. The nuclei are relatively large and 

 are placed excentrically in the cell body. There are a few cells 

 of about the same size in which two nuclei are present, but there 

 are no large, multinuclear giant cells. In addition to the round 

 cells there are other larger cells which vary in size and shape and 

 which contain large, clear vesicular nuclei, and some very large, 

 round cells with small nuclei which are apparently phagocytes. 



The stroma of the tumor consists of a reticulum of connective 

 tissue which contains typical spindle-shaped fibroblasts. In some 

 places there is little fibrous tissue, but in others the fibrosis is 

 quite marked. In the portions which have not undergone necrosis 

 there is a rich blood-capillary network in the stroma. 



In the necrotic portions of the tumor the cells show varying 

 degrees of disintegration, and the stroma is studded with nuclear 

 debris. In many places the large phagocytic cells are filled with 

 nuclear fragments. 



The appearance of the largest of the metastatic nodules is 

 identical with that of the more cellular portions of the tumor, and 

 there is marked necrosis and extensive invasion of the connective 

 tissue of the capsule. The smaller nodules are of much more 

 frequent development and show little evidence of necrosis. 



Smears from the tumor and from the metastases showed no 

 eosinophiles and no bacteria. Tissue cultures were not made. 



An attempt was made to transplant the tumor into a small 

 number of young guinea-pigs but it was unsuccessful. However 

 as I knew nothing of the tumor until about two hours after the 

 animal had died it was not possible to make the inoculations soon 

 enough to justify any hope that they would be successful. 



