Answer: Epithelioid hemangioma

Histology: The lesion consists of a central vessel involved by tumor with extension of the tumor into surrounding perivascular tissue. Within the center of the vessel, the lesion has the morphology of epithelioid hemangioendothelioma. Epithelioid cells are identified with a vacuolated appearance. The cells are seen invading through the vessel wall. However, within the surrounding tissue exterior to the vessel, the tumor forms more well-defined vascular structures. These vessels are noted for very plump endothelial lining, with an epithelioid appearance.

Discussion: If the entire lesion consisted of cells with the morphology seen within the center of the vessel, this lesion would be classified as an epithelioid hemangioendothelioma. However, if one looks only at the tumor outside of the vessel, it has a classic appearance of epithelioid hemangioma. The presence of swollen endothelial cells, some with a “tombstone” appearance, is classic for epithelioid hemangioma. The lesion lacks the interanastomosing vascular channels or cytologic atypia seen within angiosarcoma. Cellular hemangiomas do not have the epithelioid appearance as seen in the current cases. It is a recognized phenomenon that epithelioid hemangioma, a benign entity, may originate within vessels. When it originates within vessels, within the center of the lesion within the vessel, it may have the appearance of epithelioid hemangioendothelioma. Consequently, the zonation seen in the current case is totally consistent with the benign lesion epithelioid hemangioma.