Desmoplastic melanoma: a rare variant with challenging diagnosis.

Desmoplastic melanoma, a distinct and uncommon variant, is characterized as an invasive lesion with proliferation of fusiform melanocytes in the dermis and subcutaneous tissue, associated with varying patterns of desmoplasia. Neurotropism and neural differentiation may occur. The clinical presentation is variable and nonspecific, easily confused with other fibrous neoplasms. The disease is locally aggressive and shows lower metastasis rates than other types of melanoma. Histopathology may be insufficient, requiring positive immunohistochemistry for S-100 protein and other antigens of melanocytic differentiation. Because desmoplastic melanoma represents a true clinical, dermoscopic, and histopathological diagnostic challenge, a case of invasive desmoplastic melanoma is reported, affecting a photoexposed area in an elderly woman after histological revisions and an initial diagnosis of fibroma.