Desmoplastic melanoma of the nail.

Desmoplastic melanoma represents a variant of melanoma that is difficult to diagnose because 71% of patients have amelanotic skin lesions. In the acral region of the limbs, the clinical diagnosis is more difficult, especially in cases in which there are not clear, rapidly growing, pigmented nail streaks. Histopathological identification of desmoplastic melanoma is confusing because of the intense fibrous reaction in the dermis and minimal, atypical melanocytic proliferation at the dermal-epidermal junction. For these reasons, it is still misdiagnosed unfortunately as a variety of entities, including simple scar, fibrohistiocytic neoplasms, neural tumors, and superficial fibromatoses-with potentially devastating consequences. In equivocal cases, the use of immunohistochemistry (in particular S-100 and neuron-specific enolase) may be helpful in establishing the diagnosis. Because of the high local recurrence rate for desmoplastic melanoma of the finger, amputation is recommended in an effort to gain effective tumor control. Lymph node dissection may be reserved for patients with positive axillary nodes.