Acral lentiginous melanoma comprises fewer than 5% of all melanomas. This subtype is the most common type of malignant melanoma among Asians and dark-skinned individuals, often found in the soles of the feet. This melanoma is also commonly found on palmar, plantar, subungual, and occasionally, mucosal surfaces. It can also arise from the nail matrix, known as subungual melanoma, and this presents as a longitudinal brown or black band, with or without nail dystrophy. The involvement of the proximal nail fold known as Hutchinson’s sign is considered a clue to the diagnosis. On physical exam, an acral lentiginous melanoma appears as an unevenly pigmented patch, usually dark brown to black.
Coleman WP, Loria PR, Reed RJ, Krementz ET. Acral lentiginous melanoma. Arch Dermatol. 1980;116(7):773-6.