Giant congenital nevi: a conceptualization of patterns

Patterns in giant congenital nevi are classified as to extent of cellular involvement of the reticular dermis and by the quality of the fibrous matrix. In addition, classifications are influenced by degrees of cellular atypia. Two general categories are defined. In one, the phenomena are relatively independent of those operative at the dermal-epidermal interface. The lesions are characterized as dermal congenital tumorous dysplasias-blastomas. They are subdivided into major, intermediate, and minor categories and into mature and immature variants. In these variants, disparate populations in the patterns of nodules and plaques (lumpy-bumpy variants) qualify as dermal variants of minimal deviation melanoma as seen in the setting of giant congenital nevi. The respective melanomas in this category are small-cell malignant neoplasms (melanoblastomas of infancy and childhood). In a second category in the clinical setting of giant congenital nevus, rare childhood and some adult melanomas of a more common histologic type evolve from lentiginous and junctional components in patterns that recapitulate those of the dysplastic nevus syndrome. The suspicious areas in all categories are evaluated by the same clinical criteria. In the dysplasia-blastoma category, enlarging nodules must be biopsied. The criteria for the evaluation of lesions in the dysplastic nevus syndrome and in the category of minimal deviation melanoma have application to the unstable regions in giant congenital nevi.