Common acquired melanocytic nevi, melanocytic dysplasia and malignant melanoma. A morphometric study.

Nuclei of melanocytes in 10 common acquired melanocytic nevi, 10 malignant melanomas and 10 dysplastic melanocytic nevi (melanocytic dysplasia) (MD) were morphometrically analyzed. MD group consisted of 6 lesions with (MD 1) and 4 without (MD 2) the clinical features of dysplastic nevi. The considered parameters were area, perimeter and form Ar. In the MD group, the results showed that median values of each considered parameter of MD 1 were close to those of MD 2. For each evaluated parameter, median values of MD turned out to be intermediate between those of common acquired melanocytic nevi and of malignant melanomas. Confirming the histologic evidence of a double - nonatypical and atypical - melanocytic population in melanocytic dysplasia, our data showed that nonatypical melanocytes were indistinguishable from melanocytes of common acquired nevi, while the atypical melanocytes were close to melanoma cells. The importance of atypical melanocytes is stressed in the diagnosis of melanocytic dysplasia.