Nov., 1917] 



Tumors in Dogs 



of this growth. It measures ;^ x 2 x 15 cm. and is attached by 

 a pedicle 1 cm. in diameter to the gum margin between the 

 incisor teeth. It is firm, and covered by a mucous membrane 

 of normal color, except at the extreme tip, where the covering 

 has taken on a warty appearance. The tumor is not ulcerated 

 at any point. 



Microscopal examination reveals a fan-shaped section cov- 

 ered except at the point of attachment of the tumor by a normal 

 appearing epitheUum. The outer half of the tumor is composed 

 of normal appearing fibro-blasts. Just beneath this in the 

 connective tissue is a zone of giant cells. 



Fig. 2. Giant cells containing reticular fibrils. 



The distinctly neoplastic cells are more closely packed in 

 the pedicle of the tumor. While there has occurred an elabora- 

 tion of inter-cellular substances in this area, they are not so 

 rich in amount as in the older portion of the tumor. There is, 

 however, a sufficient degree of differentiation on the part of the 

 connective tissue cells composing the tumor in this growing 

 portion to place it among the benign fibroblastomas. 



Giant cells are generally thought to be produced by fusion 

 of cells or else by division of the nucleus without a corresponding 

 division of the cell body. Mallory ('11) has called attention 

 to the presence of both types in sarcomas. Those, which are the 

 product of an incomplete multiple mitosis of the tumor cells, he 

 calls "The true tumor giant cell." These are much less 

 frequently found than the other type and are indicative of 

 the rapid rate of growth of the tumor. Since a careful search 

 fails to reveal any evidence of mitosis in any of the nuclei 

 of the giant cells seen in this specimen, it is probable that 

 these belong to the fusion type of giant cell. 



It is usually stated that the type of giant cells due to fusion 

 is most frequently found in tumors associated with bone. 



