Proximal-type epithelioid sarcoma of the vulva: relationship to malignant extrarenal rhabdoid tumor.

Proximal epithelioid sarcoma is an extremely uncommon lesion of the vulva, with the potential for aggressive behavior. We report a case of this entity and discuss its relationship to the epithelial-type "malignant rhabdoid tumor" (MRT) of the soft tissue. On the basis of a review of the pertinent information on both these entities, it is concluded that they likely represent biologically different but morphologically and immunohistochemically similar neoplasms. Both proximal epithelioid sarcoma and MRT comprise epithelioid cells with densely eosinophilic cytoplasmic inclusions, and they each lack the INI1 gene product. Nevertheless, the literature suggests that other selected genetic differences between the 2 lesions, and the more rapid and aggressive course of MRT distinguish these tumor types as separate clinicopathologic entities.