Histiocytoid (epithelioid) hemangioma of the testis. The so-called vascular variant of "adenomatoid tumor".

Adenomatoid tumors are well-recognized neoplasms generally considered to be of mesothelial derivation. We describe an unusual vascular neoplasm that arose in the testis of a 29-year-old and resembled an adenomatoid tumor by light microscopy. An orchiectomy was performed, and the patient is alive and disease-free 3 years later. The 2-cm tumor was composed of small tubules lined by mesothelial-like cells with uniform, vesicular nuclei. However, some lumina contained erythrocytes, and immunohistochemically, the luminal cells reacted with antibodies to vimentin, Factor VIII-related antigen, and Ulex europaeus I lectin but not cytokeratin or epithelial membrane antigen. A cuff of muscle-specific actin-positive cells surrounded the luminal cell layer. This adenomatoid-like vascular neoplasm is more properly interpreted as a histiocytoid (epithelioid) hemangioma. Although some authors have considered microscopically similar lesions to represent a vascular variant of adenomatoid tumor, we prefer to reserve the term "adenomatoid tumor" for microscopically appropriate proliferations that have mesothelial features.