Architectural features in melanocytic lesions with cellular atypia

According to the quantity of single atypical melanocytes at the dermoepidermal junction 334 nevi were assigned to 3 groups: (1) with pronounced nuclear and cellular atypia (n = 73); (2) with moderate atypia (n = 127), and (3) without atypical melanocytes (n = 134). Three architectural features were almost exclusively observed in groups 1 and 2 with cellular and nuclear atypia: atypical localization of melanocytes in the epidermis, irregular distribution of melanocytes in the junctional zone and atypical nests of melanocytes. A combination of 2 or 3 of these features was seen in 76% of the nevi with pronounced cellular and nuclear atypia, in 28% of those with moderate atypia and in none of those without atypical melanocytes. Regarding 4 other criteria only minor but still statistically significant differences were found between the 3 groups of nevi. We conclude that these 4 other criteria, i.e. inflammatory infiltrate, lamellar and/or concentric fibroplasia, persisting lentiginous hyperplasia and dust-like pigment in melanocytes and nevus cells are not helpful for the diagnosis of a dysplastic nevus because of their low specificity. Minimal requirements for the diagnosis of a dysplastic nevus are suggested.