HMB-45 staining of dysplastic melanocytic nevi in melanoma risk groups.

To evaluate the hypothesis that reactivity of the intradermal component of melanocytic nevi to the monoclonal antibody HMB-45 correlates with melanoma risk, dysplastic compound melanocytic nevi were examined for expression of the HMB-45 epitope in three subject groups differing in epidemiological risk for melanoma. The study groups consisted of 10 subjects with dysplastic nevi and a personal history of melanoma, 25 subjects with dysplastic nevi and a history of melanoma in one or more first degree relatives, and 15 population control subjects with sporadic dysplastic nevi. For each case, sections from one lesion, immunohistochemically processed for HMB-45 binding, were evaluated by two pathologists without knowledge of the clinical data. Of all dysplastic nevi, 98% showed diffusely positive cytoplasmic staining of the junctional nevomelanocytes and 90% had such positive staining of those cells within the superficial dermis. Nevus cells within the deeper dermis did not stain positively in any case. Furthermore, the data showed no differences in frequency, pattern, or intensity of HMB-45 reactivity between the subject groups. These observations indicate that evaluation of dysplastic nevi with the monoclonal antibody HMB-45, an apparent marker of proliferative or otherwise stimulated melanocytes, has no discriminating value for identifying subjects at increased historical risk for melanoma. The data, however, support the concept that so-called dysplasia within nevi, as defined by histologic criteria, actually represents the active or proliferative phase of melanocytic nevi.