ABSTRACT
Melanoma is a malignant melanocytic tumor that represents the most frequent cause of deaths associated with skin cancer. Several classifications have been proposed, based on clinical features, histopathologic alterations, and different anatomical locations. Traditionally, four main types of melanoma are described: superficial spreading, nodular, lentigo maligna melanoma, and acral lentiginous melanoma. The differential diagnosis of conventional melanoma includes other pigmented skin tumors, mainly nevi, seborrheic keratosis, and pigmented basal cell carcinoma. The clinical discrimination between nevi and melanoma is basically based on the natural symmetry of nevi, in contrast to the irregular morphology that typifies melanoma after a certain progression point. Acral melanoma (AM) is the most common subtype of melanoma in dark-skin and Asian populations. AM has long been associated with a worse prognosis compared to other melanoma subtypes, but recent data highlighted that this is rather a result of delayed diagnosis than indicative of more aggressive biological behavior.
