2>22 



VETERINARY PATIIOEOC 



lular infiltration into dense areolar tissue. Small blood vessels 

 may be present, but the blood supplv is usually very limited and 

 the vessels occur only in the stroma. 



Microscopically, these tumors are found to consist of embry- 

 onic epithelial cells arranged in nests, the cells having no inter- 

 cellular substance between them. The cells are variable in size 

 and in shape, they may be s(|uamous, spherical or columnar. The 

 nucleus is usually much smaller in proportion to the size of the 

 cell than the nucleus of sarcoma cells. The stroma is usually 





P^ig 175 — yirliun of Ma\Ular.A C'ar<-in4inia of a horsr. showing: the iioSl 

 of <_pithi_lial Lx Us surrouncled ^J\■ a stroma. 



apprr.priated fmni the jire-existing tissue and therefore is vari- 

 able in quantity and structure. In some cases sarcomatous tissue 

 constitutes the stroma. The stroma forms alveoli in which the 

 carcinoma cells occur. In fact, the alveoli are, in many instances, 

 simply dilated lymphatic spaces wdiich have been invaded by 

 carcinoma cells. Lymph is usually quite abundant and bathes 

 the nests of the carcinfima cells in th.e alveoli. Because of the 

 freedom of anastomosis of lymph spaces and the constant flow of 

 lymph, carcinoma cells are easih- and rapidlv diffused. Karvo- 

 kinetic figures are of common occurrence in rapidly growing 

 carcinomata. There is usuall)' an inflammatory reaction accom- 



