Acral Melanoma

Abstract

Acral melanoma is defined as melanoma affecting the palms, soles, and nail apparatus. This is not a synonym of acral lentiginous melanoma in Clark’s classification, which is defined histopathologically. Acral melanoma is characterized by peculiar chromosomal and genetic alterations distinct from other subtypes of melanoma. These characteristics certainly reflect its unique pathogenesis, in which sun exposure is not a major causative factor. In this chapter, genetic characteristics of acral melanoma were first summarized and its molecular pathogenesis was discussed. Amplification of CCND1 and TERT may be early events in the development of acral melanoma. Mutations of BRAF/NRAS may be also involved in the early developmental phase of acral melanoma along with KIT mutations/amplification, which can be utilized as targets by small molecular inhibitors for the treatment of advanced acral melanoma. Next, essential points in the clinical, dermoscopic, and histopathologic diagnoses of acral melanoma were described. Particularly, dermoscopy is very helpful in diagnosing primary lesions of acral melanoma by the parallel ridge pattern, which contrasts with the parallel furrow pattern found in the vast majority of acral nevi. These different pigmentation patterns suggest de novo genesis of acral melanoma, namely, melanoma and nevus arise independently in this anatomical site. Finally, management of acral melanoma is discussed, including some suggestions in the surgical treatment and recently introduced molecular targeting therapies.