Atypical histologic features in melanocytic nevi

The atypical histologic features considered to be specific to dysplastic (a typical) nevi have been reported to occur in nevi that are common nevi by a ll other clinical and histologic features. The distribution and mutual rela tions among such features in nevi need to be further studied. Six histologi c features (dimension > 5 mm, lentiginous proliferation, disordered nested pattern, melanocytic dyskaryosis, dermal lymphocytic infiltrate, suprabasal melanocytes) were analyzed in 253 melanocytic nevi with different clinical appearances. Atypical histologic features, found in 72% of nevi, occurred singly or formed numerous and highly variable combinations. Nevi formed a c omplex histologic spectrum comprising lesions showing a progressively incre asing incidence of atypical features rather than two classes (common and dy splastic nevi). To divide the investigated lesions in objectively defined g roups, we used a scoring system. In each nevus, a numeric value of 1 was as signed when each of the studied parameters was present and a value of 0 was assigned when each of these parameters was absent; on the basis of the fin al scores, nevi were divided in six different classes (classes 0-5). Diagno stic categories such as dysplastic nevi and common nevi seem to be inapprop riate. as they do not reflect the real histologic complexity of such lesion s.