Acral lentiginous melanoma.

Acral lentiginous melanoma is an uncommon skin malignancy that occurs with equal frequency in all races and has a worse prognosis than other types of melanoma; it presents as dark, irregular macules, papules, or nodules on the feet and, less commonly, the hands. The histologic findings of acral lentiginous melanoma are characterized by an asymmetric, poorly circumscribed proliferation of continuous single melanocytes at the dermoepidermal junction. Single melanocytes predominate over nests. The tumor must be distinguished from benign acral lentiginous nevi, which can display site-related atypia.