Anastomosing Hemangioma: Short Review of a Benign Mimicker of Angiosarcoma.

Anastomosing hemangioma is a rare neoplastic vascular lesion, histologically mimicking angiosarcoma. It is predominantly composed of irregularly anastomosing sinusoidal-like spaces lined by endothelial cells with minimal atypia, a frequently hobnail morphology, and minimally invasive margins. Since its original description in the genitourinary system, an increasing number of anastomosing hemangiomas have been reported, localized deep in the body in various organs, always with similar histologic features. It is more frequently asymptomatic, often discovered incidentally by imaging studies, owing to coexisting benign or malignant tumors. In renal cases, the most frequent clinical context is end-stage renal disease. There is overwhelming evidence of the benign nature of the lesion and an accurate diagnosis could prevent overtreatment. The differential diagnosis includes other benign vascular tumors, well-differentiated angiosarcoma, Kaposi sarcoma, and other vascular-rich neoplasms. We review the clinical and histopathologic characteristics of this peculiar lesion with an emphasis on the differential diagnosis.