The precursors of malignant melanoma.

The precursors to melanoma are generally considered to be related to nevi of different types. Here we emphasize the dysplastic nevus, the congenital nevus, and lentigo maligna as specific lesions. The dysplastic nevus is discussed not only as a formal precursor but also as a marker of cutaneous melanoma. The clinical and histologic characteristics are outlined, as well as evidence of progression in dysplastic nevi. The congenital nevus is briefly reviewed and emphasis is placed upon clues to malignant degeneration. The concept of lentigo maligna as a precursor as distinct from an in situ phase is detailed.