2 20 BIOLOGY OF THE LABORATORY MOUSE 



True adenomas of the liver parenchyma cells occur most frequently in the 

 C57 black, yellow, and dba stocks but are not limited to them. These 

 tumors are circumscribed growths of atypical parenchyma cells with atypical 

 arrangement but without signs of infiltration or marked activity. Slye (51) 

 found a few similar tumors. Carcinoma of the liver is encountered quite 

 often among our primary liver tumors. The usual picture is of large and 

 small liver parenchyma cells growing in wild confusion with frequent tumor 

 giant cells and bizarre cell forms (Fig. 119). Normal architecture is lost and 



b.v. 



m.f. 





Fig. 119. — Carciiuuna ui iht- liver parenchyma cells (xjoo). Ij.v., blood vessel; 

 h.s., hepatic sinusoid; m.f., mitotic figure; p.c, tumorous liver parenchyma cells. 



invasion of adjacent normal liver occurs. Mitoses may be frequent and 

 metastasis to the lung occurs. The tumors of the liver parenchyma cells 

 appear grossly as elevated or pedunculated masses that are almost the same 

 color as normal liver. There is a rare form of carcinoma of the liver com- 

 posed of large, pale cells whose arrangement suggests attempted gland 

 formations. Mitoses are frequent. Papilloma of the gall bladder has been 

 observed. 



Non-epithelial liver tumors are also seen somewhat frequently. Tumors 

 of the lymphoid, myeloid, and monocyte cells are taken up elsewhere. 

 Hemangiomas are a fairly common type of liver tumor, and hemangio- 

 endotheliomas are occasionally observed in some stocks. A lymphangio- 



