202 



BIOLOGY OF THE LABORATORY MOUSE 



cells are flattened and pavement like. The spaces are blood filled and irregu- 

 lar in size and shape (Fig. iiiA and B). Only narrow septa of fibrous con- 

 nective tissue stroma are present between the spaces. Epithelial elements do 

 not appear as a part of these tumors. Within the tumors foci of thrombosis 

 and considerable old blood pigment are often seen. The connective tissue 

 capsule is not wtU formed. Mitotic figures are rare. In mice this tumor 



Fig. III. — Hemangioma 



A, shows typical arcliiteclure (. X50) 

 endothelial lined spaces (X200). 



tilled 



frequently shows a mixture of capillary -like and cavernous blood filled 

 spaces. 



Lymphangioma is most often found in the axillary and the inguinal 

 regions. Sometimes it occurs near these sites where it may have originated 

 from lymph nodes. Irregular, large or small lymph filled sinusoidal spaces 

 are seen lined by flattened endothelial cells. The connective tissue stroma 

 forms nodular septa containing small lymph vessels and normal appearing 

 lymphocytes in varying degrees of concentration. In its most benign form 

 this tumor exhibits broad bands of connective tissue stroma surrounding 

 long, narrow, irregular, endothelial-lined spaces filled with lymphocytes. 

 This may involve a large part of a lymph node. 



