Ki-67 and p53 Expression in Minimal Deviation Melanomas as Compared with Other Nevomelanocytic Lesions

Abstract

Minimal deviation melanoma is a controversial entity encompassing a heterogeneous group of lesions cytologically in the spectrum between recognized subtypes of nevi and conventional “primary configuration” melanomas and reported to have a better prognosis than the latter. To evaluate the distinctiveness of minimal deviation melanoma, Ki-67 proliferation rates and p53 expression in minimal deviation melanomas were compared with those in compound nevi, Spitz nevi, and vertical growth phase superficial spreading malignant melanoma. Twelve examples of each lesion were immunostained with antibodies to the Ki-67 and p53 proteins and evaluated by a pathologist who was blind to the diagnoses. The mean Ki-67 (MIB-1) proliferation rates for the compound nevi, Spitz nevi, minimal deviation melanomas, and superficial spreading malignant melanomas were 0, 3%, 13%, and 25%, respectively. The mean Ki-67 proliferation rate was statistically greater in the minimal deviation melanomas than in the compound nevi or the Spitz nevi (P < .05), but the proliferation rates in the two melanoma subtypes were not statistically significant (P = .08). The mean p53 values for these lesions were 0, 9%, 9%, and 26%, respectively; the latter two were statistically different (P < .01). Based on these Ki-67 and p53 immunophenotypes, minimal deviation melanoma may represent a distinct entity.