Melanocytic atypia in dysplastic nevi. Immunohistochemical and cytophotometrical analysis.

In a double-blind study a correlation was found between the histologically assessed degree of nevomelanocytic atypia in 58 dysplastic nevi (DN) and the presence of two markers associated with malignant transformation. The markers included a marked expression of histocompatibility locus Class I antigens on nevomelanocytes (P less than 0.01) and abnormalities in the nuclear DNA content as measured by DNA cytophotometry (P = 0.01). Both markers were present in most of the markedly atypical DN, in about half of the moderately atypical DN, and in less than 30% of the mildly atypical DN. These findings suggest that a DN with marked or moderate melanocytic atypia indicates a premalignant condition and identifies a patient at risk for melanoma.