A case of desmoplastic melanoma

Abstract

Desmoplastic melanoma is a rare variant of the spindle cell melanoma that first was recognized and described in 1971 as an invasive fibrosarcoma-like tumor that exhibits an abundant collagenous stroma. These tumors usually arise in sun-damaged skin of the head and neck in older persons, in association with lentigo maligna or de novo. The clinical presentation is often not characteristic, and they may clinically simulate other tumors of the skin. Hence they are often diagnosed late. Histologically, desmoplastic melanoma appears as a nodule of fibrous tissue containing hyperchromatic pleomorphic spindle cells that either are scattered singly, lie in fascicles, or aggregate in nests, and collagenous tissue replacing the reticular dermis. Immunohistochemistry is usually quite helpful as the tumors are almost always immunoreactive with S-100 protein and negative for HMB-45. We report a case of desmoplastic melanoma in a 67-year old male who had a walnut sized tumor upon large indurated plaque on the left thigh. A biopsy specimen of the tumor showed that fascicles of spindle cells are interspersed throughout collagenous tissue and most tumor cells are immunoreactive with S-100 protein. To our knowledge, this is the first case report in Korea.