[Melanoma of soft tissues]. / Mélanome des tissus mous.

INTRODUCTION: Soft tissue melanoma was described in 1965 by Enzinger who used the term clear-cell sarcoma. In 1983, Chung and Enzinger coined the term soft tissue melanoma due to the immunohistochemical similarity with melanoma. We report a case of this rare type of melanoma. CASE REPORT: A 59-year-old woman had pain between the first two toes for 3 years. A subcutaneous tumor was found at examination. Histologically, the tumor was composed of weakly eosinophilic cell proliferation. Protein S100 and HMB45 were positive. The cells were organized in theques. Pathology diagnosis was soft tissue melanoma. Complete remission was obtained for 3 years when several local recurrences required surgery and chemotherapy then surgery and radiotherapy. Complete remission has been achieved for 9 months. DISCUSSION: This case presented the main characteristics of soft tissue melanoma as described in a review of 209 analyzable cases reported in the literature. This tumor occurs in young subjects with no sex or race predominance. It is an ubiquitous tumor which develops in close relation with tendons and aponevroses, usually in limbs (especially feet). Pain is sometimes the revealing manifestation, but the tumor is often asymptomatic, so the volume is often important at diagnosis. Pathology examination shows rather monomorphic proliferation of cells with a clear or weakly eosinophilic cytoplasm grouped in clusters or theques separated by fibrous septa. Intracytoplasmic melanin is sometimes observed, indicating interest of protein S100 and HMB45 immunohistochemistry which is almost always positive. The principle differential diagnoses are metastasic melanoma and epithelioid sarcoma. Prognosis of soft tissue melanoma is similar to that in sarcomas with a high rate of local recurrence and metastases (lymph nodes, lungs). Mortality reaches 56 p. 100. Treatment is wide surgical exeresis. CONCLUSION: Soft tissue melanoma is a rare tumor of the melanocyte. It differs from melanoma by the population involved, its clinical expression and its prognosis which is similar to that in sarcoma.