Acral lentiginous melanoma of the oral cavity.

Lentiginous melanomas may be classified clinicopathologically as either lentigo maligna melanomas or acral lentiginous melanomas. Lentigo maligna melanoma is generally characterized by its slow rate of growth, lateness of metastasis, and relatively good prognosis. Acral lentiginous melanoma, while demonstrating a radial growth phase which is histologically similar to that of lentigo maligna, appears biologically more similar to superficially spreading malignant melanoma once the vertical growth phase supervenes. Mucous membrane melanomas with lentiginous characteristics are likely to be aggressive lesions with a marked propensity for metastasis and a uniformly poor prognosis, much like the acral lentiginous type of melanoma. It would seem, therefore, that superficial melanomas of the oral mucous membranes with a lentiginous pattern should best be termed acral lentiginous melanomas instead of lentigo maligna melanomas so as to more accurately predict their true biologic potential. An amelanotic case is presented which we believe illustrates this point.