Acral Melanoma: Review of Clinical, Histologic, and Molecular Findings.

Acral melanoma (AM) is the least common melanoma subtype, yet the most common to affect African American populations. Its prognosis is worse than other melanoma subtypes, chiefly owing to delayed diagnosis related to myriad clinical presentations compounded by delayed awareness of this entity in darkly pigmented individuals, leading to advanced stage at diagnosis. Distinctive histologic findings include lentiginous, single-cell growth of melanocytes, which may be subtle, and diagnosis is aided by immunohistochemistry. Unique molecular alterations include low tumor mutation burden and high number of copy number variations, often resulting in amplification of genes CCDN1 and KIT and TERT translocations.