Rectal angiolipoma diagnosed after surgical resection: a case report.

Angiolipoma is a common benign tumor with a characteristic vascular component that usually occurs in subcutaneous tissue. Although lipomas are frequently encountered at colonoscopy as submucosal tumors, angiolipomas are rarely found in the gastrointestinal tract including the large intestine. Here we report a 77-year old Japanese man who underwent transanal resection of a tumor that was diagnosed tentatively as a leiomyoma. Histologically, the tumor consisted of mature fat cells and blood vessels. Immunohistochemically, the tumor cells were negative for c-kit and HMB-45, which are consistently expressed in tumors such as gastrointestinal stromal tumor and angiomyolipoma. The tumor was therefore diagnosed as an angiolipoma. This is thought to be the first case report of a surgically resected angiolipoma of the rectum.