1 98 BIOLOGY OF THE LABORATORY MOUSE 



males and females, most commonly in the A stock. They are also seen 

 arising from the preputial glands of the male (23) and the clitoral glands of 

 the female mouse. The chief characteristic is the resemblance of the cells 

 to the normal cells of the sebaceous glands. They are large round cells with 

 pale cytoplasm which appears to be filled with fine droplets (Fig. 109). The 

 nuclei are relatively small, pale, oval and centrally located. These tumor 

 cells grow in irregular masses as well as in broad branching strands. The 



-Epithelial pearl 



-Polyhedral cells 



Undifferentiated tumor 

 cells 





^ , _. . ,_.- « . , Pearl with keratohyalin 

 i^*"*jkf^ .♦ T> j granules 







/- 



*♦'•■'- ,.■^ * 



Fig. 106. — Epidermoid carcinoma of the skin on ilie ventral abdominal surface (X200). 



most rapidly growing parts may contain small round, rather deeply staining, 

 cells which have a small amount of cytoplasm and oval nuclei. These cells 

 resemble the small undifferentiated cells of epidermoid carcinomas. Some- 

 times stratified squamous cells are found in some of the tumors of the clitoral 

 glands. Since the smaller tumor cells may also rather closely resemble small 

 undifferentiated cells of carcinoma of the mammary gland, it is not always 

 easy to determine whether one is looking at a carcinoma of the clitoris or a 

 carcinoma of the mammar\^ gland invading the clitoral glands. Both of 

 these conditions do occur. Usually the clitoral glands show active growth 

 with dedifferentiation when they are the primary site of the neoplasm. 



