Proximal-type Epithelioid Sarcoma of the Pelvis

Abstract

Epithelioid sarcoma is a rare malignant soft-tissue sarcoma with an unknown histiogenesis, typically presenting as a subcutaneous or deep dermal mass lesion in the distal portions of the extremities of young adults. Recently, a more aggressive, so-called 'proximal-type' epithelioid sarcoma has been reported. In contrast to conventional epithelioid sarcoma, the proximal type is characterized by a predominantly large cell epithelioid cytomorphology, marked cytologic atypia, and frequent occurrence of rhabdoid features in most patients. Proximal-type epithelioid sarcoma has a predilection for appearing in the genitalia, especially the vulva, penis, pelvis and buttocks. Also this lesion appears to be somewhat more aggressive or at least metastasizes earlier than the conventional epithelioid sarcoma. We report a 13-year-old girl who presented with a huge mass filling the pelvic cavity which was painful, hard and fixed on palpation, and was radiologically diagnosed as a malignant germ cell tumors on the CT scan. The mass was surgically excised and pathologically proved to be an proximal-type epithelioid sarcoma of unknown origin.