Dysplastic changes in different types of melanocytic nevi. A unifying concept.

We observed histopathologic changes previously described in dysplastic melanocytic nevi in association with a dermal component characteristic of other types of melanocytic nevi or overlapping with features of other varieties of nevi. In order to determine the frequency of these changes, we studied 2,164 cases of compound melanocytic nevi that fulfilled the histopathologic criteria for the diagnosis of compound dysplastic nevus, including architectural pattern, cytologic features, and mesenchymal changes. Of the 2,164 compound dysplastic melanocytic nevi, 1,895 (87.6%) had the histopathologic characteristics previously described for dysplastic nevus, 179 (8.3%) showed a dermal component with a congenital pattern, 67 (3.1%) demonstrated epidermal and dermal characteristics of Spitz's nevus, 8 (0.3%) had features of a combined blue nevus, 13 (0.6%) had a halo phenomenon and 2 (0.1%) showed dermal neuronevus. By considering these nevi as variants of dysplastic nevi, one may apply a unified conceptual basis for their nomenclature. In order to completely describe the appearance of the nevus, we named them by adding the term "dysplastic", to their main histopathologic subtype. Accordingly, six different varieties of dysplastic nevi were identified: 1) dysplastic nevus (original); 2) dysplastic nevus with a congenital pattern; 3) dysplastic Spitz's nevus; 4) dysplastic combined blue nevus; 5) dysplastic halo nevus; and 6) dysplastic neuronevus. In summary, we conclude that the histopathologic criteria previously reported for the diagnosis of dysplastic nevi may be found in association with a dermal component characteristic of other types of melanocytic nevi or may have overlapping features with other variants of nevi.