SPONTANEOUS NEOPLASMS IN MICE 



193 



cells. The architecture exhibits the same characteristics as are described 

 under fibrosarcomas of the subcutaneous tissue in general. Mammary 

 glands are present around this tumor and usually are invaded by the 

 infiltrating tumor mass. 



Tumors in or Near the Mammary Line and Its Branches but Not 

 Originating from the Mammary Gland Proper 



Tumors in or near the mammary line and its branches and not originating 

 from mammary glands or their stroma may be either benign or malignant. 

 While such tumors are in no essential way different from tumors in general 



Carcinomatous foci 



Sarcomatous focus 



Fig. 103. — Carcinosarcoma of the mammary gland (X200). 



which are found subcutaneously, it is convenient to list and briefly describe 

 them here because of the fact that confusion with true mammar}- tumors is 

 possible if diagnosis is not carefully made. Normal appearing mammar\- 

 glands are found either adjacent to or invaded by these tumors. For the 

 details of their histological appearance the reader should turn to the section 

 on Tumors of the Dermis, Subcutaneous and Body Wall Tissues (p. 199). 

 Only the names and a brief description are given below. 



Fibromas, chondromas and osteomas.— These originate from fibrous 

 connective tissue, cartilage and bone respectively and are uncommon in this 



