[Report of a case of adenomatoid tumor in the epididymis]

A case of adenomatoid tumor arising from the epididymis is reported. A patient visited our hospital with complaint of a painless intrascrotal mass. Preoperative diagnosis was right epididymal tumor. Right epididymectomy was performed and histological diagnosis was adenomatoid tumor of the epididymis. We examined the histogenesis of this case by the immunoperoxidase technique. The tumor revealed cytoplasmic staining of tubular lining cells for keratin with no staining for myoglobin. This finding supported a mesothelial rather than endothelial derivation for this tumor. We found no muscle elements in this tumor.