Subungual melanoma: a deceptive disorder.

Subungual melanoma is an uncommon form of acral melanoma that arises within the nail bed. The incidence for acral melanomas is similar worldwide, but the proportion is higher in dark-skinned individuals. The subungual form represents about 2% of cutaneous non-sun induced melanomas in the western world, and up to 75% in Africans, 10% in Japanese, and 25% in the Chinese of Hong Kong. Up to 33% of subungual melanomas are amelanotic. Black pigmentation of the adjacent nail fold, termed Hutchinson's sign, may be a diagnostic clue. Non-specific features and symptoms along with a high incidence of amelanosis often lead to delayed diagnosis, disease progression, and a poor prognosis with challenging treatment options.