Anastomosing hemangioma of the kidney: a case report of a rare subtype of hemangioma mimicking angiosarcoma and review of the literature.

Anastomosing hemangioma is a recently described, unusual variant of capillary hemangioma which seems to be unique for the genitourinary system, with a particular proclivity for the kidney. Histologically, it is characterized by a unique sinusoidal architecture reminiscent of splenic parenchyma that can lead to concern for angiosarcoma. We herein report a further case of anastomosing hemangioma originating in the right kidney of a 48-year-old Chinese man. The patient had a past medical history significant for hepatocellular carcinoma; this tumor was incidentally identified as an asymptomatic right renal mass during the periodical surveillance of the hepatic cancer. The resected tumor measured 2.5 cm in maximum diameter and microscopically demonstrated an overall lobulated growth pattern with alternating cellular areas composed of anastomosing sinusoidal capillary-sized vessels lined by hobnail endothelial cells, and edematous, hyaline paucicellular areas. Cytologically the tumor cells were generally bland and exhibited positivity for CD31, CD34 immunohistochemically. The patient had been in a good status without evidence of tumor recurrence 12 months after the surgery. This rare variant renal hemangioma is in need of more recognition and should not be over-diagnosed as a malignance, particularly angiosarcoma.