Unclassified epithelioid vascular tumor with hemangioendotheliomatous features and lymphatic differentiation.

Reported herein is an unusual vascular tumor that arose in the little finger of a 10-year-old boy. The tumor consisted of a vaguely demarcated nodular mass, which was located in the subcutaneous layer and measured 1 cm in diameter. Microscopic characteristic findings of this tumor were epithelioid nests, admixed with focal components with retiform features, intraluminal papillary tufts, and spindle cells. These features resemble those of subtypes of hemangioendotheliomas. On immunohistochemistry CD31, CD34 and D2-40 were diffusely expressed in the tumor cells, representing prominent lymphatic differentiation. These findings are not characteristic of any established types of vascular tumors. The differential diagnosis for the current peculiar tumor are discussed.