There is general agreement that large congenital nevi should be completely excised, when feasible. Multiple serial excisions may be necessary. Several clinical types of melanoma have been recognized. Lentigo maligna melanoma and superficial spreading melanoma are characterized by an early horizontal growth phase in the epidermis, which is followed after a variable period by dermal invasion that results in a nodular lesion. Acral lentiginous melanoma occurs on palmar, plantar, and mucosal surfaces.
Nodular melanoma arises directly in the vertical growth phase with dermal invasion.
Lentigo maligna melanoma, also known as Hutchinson freckle, occurs in elderly patients who have a history of a premalignant lesion called lentigo maligna. The lesion often appears on the face or on other areas exposed to the sun. Histologic features include cellular pleomorphism with the juxtaposition of normal and bizarre melanocytes, principally in the basal epidermis. There is diffuse intraepidermal distribution of relatively monomorphous, large malignant melanocytes in noninvasive areas. Lesions are more common in patients older than 60 years.