Acral lentiginous melanoma is a type of melanoma arising on the palms or soles. It is a form of melanoma characterised by its site of origin: palm, sole, or beneath the nail (subungual melanoma). It is more common on feet than on hands. It can arise de novo in normal-appearing skin, or it can develop within an existing melanocytic naevus (mole).
Acral lentiginous melanoma starts as a slowly-enlarging flat patch of discoloured skin. At first, the malignant cells remain within the tissue of origin, the epidermis. This is the in situ phase of melanoma, which can persist for months or years.
Acral lentiginous melanoma becomes invasive when the melanoma cells cross the basement membrane of the epidermis and malignant cells enter the dermis. A rapidly-growing nodular melanoma can also arise within acral lentiginous melanoma and proliferate more deeply within the skin.