SPONTANEOUS NEOPLASMS IN MICE 



i»3 



section or near this angle. Mitoses are frequent and infiltration around and 

 into normal adjacent structures, such as muscle and nerves, can be seen. 

 Small central islands or scattered peripheral foci of other forms of mammary 

 carcinoma are often seen in this type of tumor. The outstanding character- 

 istics are the uniformity in size and distribution of these small duct-like, 

 coiled structures lined by one or two layers of small, cuboidal epithelial 

 tumor cells. 



Adenocarcinoma (variable type). — This shows gland-like formations 

 which may exhibit a wide range of size, arrangement and degree of similarity 





Wui m 



'f-'H ■ 





Tubules of carcinoma 



Stroma 



Sinusoidal blood space 



Fig. 95. — Simple adenocarcinoma of the mammary gland showing small duct- 

 like cancer tubules (X200). The area illustrated shows more stroma than is usually 

 observed. 



as compared to the normal mammary gland. However, their origin from 

 mammary glands is always evident, since some degree of attempted gland 

 formation is a characteristic feature (Figs. 96 and 97). There is a varying 

 degree of definite lumen formation, and around this the epithelial tumor cell 

 lining ranges from one to several layers in thickness. These cells show fre- 

 quent mitoses, may be large or small, cuboidal shaped and exhibit consider- 

 able loss of normal orientation. They often grade over from glands with 

 definite lumen formations to disorganized nests of epithelial tumor cells. 



Different tumors of this type may show a variety of arrangements. One 

 may show broad, ramifying and branching strands of closely packed abortive 



