Splenic hamartoma and capillary hemangioma are distinct entities: immunohistochemical analysis of CD8 expression by endothelial cells.

The histologic and immunohistologic features of two morphologically similar splenic tumors, a capillary hemangioma and a splenic hamartoma, are reported. The hemangioma was composed predominantly of small vascular channels lined by endothelium expressing factor VIII-related antigen and lacking T-subset antigen (CD8). In contrast, the splenic hamartoma was predominantly a spindle cell lesion with numerous vascular channels coursing through the tumor; these contained splenic-type endothelium expressing both CD8 and factor VIII-related antigen. Our results justify the concept that the splenic hamartoma is a tumor of splenic origin or a true hamartoma and is distinct from the splenic capillary hemangioma.