[Malignant dermohypodermic melanoma of the soft tissues]

Melanoma of the soft tissue is a rare tumor that develops in most cases in the deep structures, only rarely involving the skin surface. We report an exceptional case of melanoma of the superficial soft tissue, exclusively involving the skin surface.

A 35-year-old man presented with a superficial, pink, soft, mobile, lesion on the thigh. The histological examination revealed a tumoral proliferation of the reticular dermis and hypodermis, composed of pale giant cells grouped in nests or in lobules separated by connective ducts. Immunostaining was positive for HMB45, protein S-100, vimentine and NKIC3. It was negative for EMA, CD34, smooth muscle actin, cytokeratine and desmine. The search for a metastatic localization was negative. Extensive exeresis was performed. Three years later, the patient was still in complete remission. The macroscopic, histological and immunohistochemical examinations concluded in the diagnosis of a strictly dermohypodermic melanoma of the soft tissues.

Our case report of a melanoma of the soft tissues is original because of the superficial localization of the tumor that, to our knowledge, has never been reported. It underlines the interest of performing systematic biopsies of any fast growing cutaneous lesion of recent discovery.