SPONTANEOUS NEOPLASMS IN MICE 219 



Monocyte sarcoma.— -This tumor is similar to the above but mitoses are 

 more frequent and the cells show more variation in size. Large tumor giant 

 cells and bizarre shaped cells are often seen. 



The writer is well aware that there is considerable difference of opinion 

 concerning the monocyte tumors. Because of this the above discussion is 

 necessarily brief and somewhat incomplete. The work now being done at 

 several institutions should be of real value in clarifying their classification 

 and nomenclature. 



Tumors of the Digestive System and Associated Glands 

 Digestive Tube and Submaxillary Gland Tumors 



Tumors of this region are rare but they do occur. In the submaxillary 

 gland we have seen an adenoma in a yellow stock mouse and a carcinoma 

 simplex in an A stock albino female. Tumors of the oral cavity and the 

 esophagus have been extremely rare (68). However, we have had a papil- 

 loma develop in the esophagus of a mouse. 



Marked hyperplasia of the epithelium in the glandular part of the 

 stomach has been observed in several of our mice. This has also been 

 recorded in other laboratories. Wells (68) reviews the literature and reports 

 three adenocarcinomas of the pylorus. Epidermoid carcinoma of the non- 

 glandular part of the stomach has been seen. Here the normal lining is 

 stratified squamous epithelium and the tumor shows definite epithelial pearl 

 formation. In a C57 black mouse this type of tumor has been observed to 

 infiltrate through the stomach wall and to begin the invasion of the pancreas. 

 Similar tumors have been recorded by Slye (54, 68) and others. 



A few intestinal polyps have occurred. In one case beginning adeno- 

 carcinoma was observed in this type of polyp. Carcinomas are rarely 

 observed, even though the intestine is inspected routinely at autopsy. In 

 Slye's laboratory a few squamous cell carcinomas and adenocarcinomas of the 

 intestine have been found (68). Cavernous hemangioma and primary 

 fibrosarcoma have been found in our C57 black, the dba mice and their 

 hybrids. Other fibrosarcomas have been seen in the mesentery of the small 

 intestine. Lymphocyte tumors also occur in the lymph nodes of the intes- 

 tines in several stocks. 



Hepatic and Gall Bladder Tumors 



The liver is a relatively common site for primar>' tumors (hepatomas). 

 Regeneration adenomas are the result of rapid proliferation as an attempted 

 repair following injury. Such lesions have not been classified as tumors. 



