Splenic hamartoma, vascular type, with endothelial proliferation.

Vascular tumors of the spleen have shown a wide spectrum of histologic features. We present the case history of a 65-year old woman with weight loss, anemia and thrombocytopenia associated with a vascular tumor of the spleen. Grossly, the tumor appeared like the red pulp of the spleen. On microscopic examination, however, a papillary proliferation of the endothelial cells which caused narrowing of the lumina of newly-formed vessels was seen. The endothelial cells further showed multiple cytoplasmic projections with few junctions under electron microscopy. In spite of the morphology the tumor proved to be benign. This appears to be the first ultrastructural study of such type of vascular tumor.