The histological spectrum of acquired nevi. An analysis of the intraepidermal melanocytic proliferation in common and dysplastic nevi.

The histological intraepidermal characteristics considered to be specific to dysplastic nevi (radial extension, lentiginous and disordered nest proliferations, cytological atypia or dyskaryosis) were investigated in a series of 114 acquired nevi showing various clinical appearances in an attempt to establish whether dysplastic nevi can be considered a homogeneous class of lesions, clearly distinct from common nevi. On the basis of the distribution of investigated architectural features, found singly or variously associated, the examined lesions were divided into 5 groups, showing an increasing incidence of dyskaryosis. Results suggest that acquired nevi, rather than two distinct classes (common and dysplastic nevi), form a histological spectrum of lesions, within which the border between lesions implying and not implying an increased melanoma risk cannot be objectively fixed.