SPONTANEOUS NEOPLASMS IN MICE 



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connective tissue and blood vessels infiltrate and can be found, by careful 

 observation, even within the finer branches of the papillae which arc com- 

 posed largely of disorganized nests and partial gland-forming foci of epithe- 

 lial tumor cells. 



stroma 



Disorganized tumor cells 



Palisading layer 



Fig. qq. — Intracanalicular adenocarcinoma of the mammary gland. A, shows typical 

 architecture (X200); B, shows the cellular detail (X400). 



Intracanalicular adenocarcinoma. — This tumor grows as finger-like 

 branching and anastomosing strands of epithelial tumor cells extending into 

 a loose stroma (Fig. 99A). The edges of these strands are smooth due to an 

 orderly paHsade arrangement of a single outer layer of epithelial cells. 

 Within this palisade layer the entire remainder of these finger-like processes 

 is composed of epithelial tumor cells of the same type and size but with a 

 disorderly arrangement due to loss of normal orientation (Fig. 99B). 



These tumor cells are closely packed and cuboidal in shape, somewhat 

 larger than normal resting mammar}^ gland epithelium, with moderately 



