1 88 BIOLOGY OF THE LABORATORY MOUSE 



hyperchromatic, oval nuclei and scant cytoplasm. The stroma consists of 

 loosely scattered, threadlike connective tissue cells and thin-walled blood 

 vessels. 



This type of tumor derives its name from its manner of growth, which is 

 intraductal, filling the lumen with wildly growing, epithelial tumor cells, but 

 having an outer layer of orderly arranged cells. This arrangement of cells, 

 together with the manner of infiltrating the stroma in branching finger-like 



Lumen 



Epithelial tumor 

 cells 



Fig. ioo. — Macroglandular adenocarcinoma of the mammary gland (X200). 



processes, constitutes the distinguishing characteristics for intracanalicular 

 adenocarcinoma. 



Mitoses are frequent. Infiltration of normal adjacent structures occurs 

 and metastases to the lungs are fairly frequent. 



Macroglandular adenocarcinoma. — This type of growth is probably what 

 Apolant (i) called fissure forming carcinoma of the mammary gland. Here 

 occurs what appears to be enormous gland-like structures with long, branch- 

 ing, irregular lumena (Fig. 100). The walls are thrown into folds and are 

 composed of four or five to many cell layers in thickness. The epithelial 

 tumor cells forming the walls are medium sized, oval and closely packed, 

 often growing in wild disorder with frequent mitotic figures in evidence. 



