MLANA and primitive neuroectodermal tumor: Clear-cell sarcoma could be ruled out by negative immunohistochemistry for HMB45, S-100 and Melan A. A previous study also indicated the necessity of distinguishing from an intraabdominal desmoplastic small round cell tumor (IDSRCT) by histological and immunohistochemical characteristics when ES/PNET occurs in the abdominal cavity [13].