Anastomosing hemangioma of the liver and gastrointestinal tract: an unusual variant histologically mimicking angiosarcoma.

Anastomosing hemangioma, a benign vascular neoplasm histologically simulating angiosarcoma, is newly recognized and has been described primarily in the genitourinary tract. We have encountered this lesion in the liver and gastrointestinal tract, where it can be diagnostically challenging, especially in core biopsy. Herein, we described 6 cases of anastomosing hemangioma of the liver and gastrointestinal tract. They occurred in 4 women and 2 men, ranging in age from 48 to 71 years. The tumors ranged from 0.2 to 6 cm (median, 3.1 cm) and were grossly well demarcated with a gray-brown spongy appearance. Microscopically, they had a loosely lobulated architecture. At higher magnification, lesions consisted of anastomosing sinusoidal capillary-sized vessels with scattered hobnail endothelial cells. Mild cytologic atypia occurred in all cases. Mitoses were absent. Vascular thrombi were seen in 4 cases (66.7%) without necrosis. One tumor (16.7%) featured prominent extramedullary hematopoiesis and 1 (16.7%) hyaline globules. Immunohistochemistry results were available for 3 cases, and the lesions stained with CD34 and/or CD31. Five cases had clinical follow-up information; there were no recurrences or metastases (range, 8 to 96 mo; mean, 41 mo), and 1 patient received no follow-up after a benign diagnosis on her colon polyp. In summary, anastomosing hemangioma of the liver and gastrointestinal tract is a rare distinctive vascular neoplasm displaying overlapping features with well-differentiated angiosarcoma. Despite small numbers and limited follow-up information in our series, evidence to date supports that the lesion is benign. Awareness of this entity is essential to avoid overdiagnosis and unnecessary aggressive treatment.