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Malignant melanoma of soft parts: A rare entity with a specific genetic marker

To theEditor:Malignantmelanoma of soft parts (MMSP) is a rare and highlymalignant neoplasia of difficult diagnosis.We describe a case of MMSP in a 14-year-old girl who was previously misdiagnosed as malignant schwannoma. The patient was referred to our unit after abdominal surgery. A non-ovarian retro-peritoneal tumor (encapsulated, 8 5 3 cm) with histological diagnosis of malignant schwannoma not involving main nerves, viscera or vessels, had been completely removed. It was S-100þ, NSEþ, Ki67> 10%, and c-KIT, CD34, Actin SMA, Actin HHF-35, Desmin negative. The girl had had a left sole tumor removed with the believe that it was a plantar wart. Threemonths later, she relapsed with an abdominal tumor that was completely removed. Histological diagnosis was consistent with a malignant schwannoma. Subsequently left popliteal and inguinal lymph node metastases were found. She was treated with surgery and chemotherapy according to a soft-tissue sarcomas protocol (MMT-95). After two courses of chemotherapy (IVA), there was no evidence of response and the treatment was stopped. Histological samples were reviewed and the chimeric EWS/ATF1 gene as result of the translocation t(12;22) (q13;q12) was documented by PCR, a finding that confirmed the diagnosis of MMSP. The disease progressed despite repeated surgical procedures and second-line chemotherapy (CDDP, Tamoxifen, Dacarbazine) and she died from progressive disease. Malignant melanoma of soft parts (MMSP), also called clear cell sarcoma is an infrequent tumor. The exact histogenesis remains unclear, but the presence of intracellular melanin supports its origin from migrated neural crest cells with capacity for producing melanin [1]. This neoplasm typically involves tendons and aponeuroses [2] of the extremities (feet, knees, wrists, etc) with propensity for lymph node [3], lung, and bonemetastases. It is an aggressive tumor, extremely rare in childhood [4] and affects mainly young women. Differential diagnosis includes other clear cell tumors [5]. This neoplasm expresses S-100, vimentin, NSE, and is reactivewith themelanoma-specificmonoclonal antibody HMB-45 [2]. The translocation t(12;22)(q13;q12) or the chimerical EWS/ATF1 gene, identified in a high percentage (50–75%) of MMSP, are presumed to be tumor specific[6]. Complete surgical resection with negative margins is the only effective treatment [7]. In non-metastatic MMSP, overall survival is 50%, with late relapses being common. Patients with metastasis should be candidates for multicentre investigational trials [7] because chemotherapy is ineffective [4] and the prognosis extremely poor [8].