Expression profile of Ki67 in palmoplantar melanocytic lesions: a case-control study

Background: Acral lentiginous melanoma is a malignant neoplasm which appears in hands and feet. Acral lentiginous melanoma has an unclear etiology, and usually affects non-Caucasian population. Because it is frequently diagnosed lately, acral melanoma has bad prognosis; however, it is biologically more aggressive than other clinicopathological types of melanoma, even when diagnosed early. Objective: To determine the expression of Ki67 in invasive lentiginous acral melanoma and to compare it with acrel nevi. Method: Cross-sectional, descriptive, observational study. Immunohistochemistry with Ki67 marker was performed on 17 biopsies of invasive lentiginous acrel melanoma (cases) and 17 biopsies of palmoplantar nevi (controls). Nuclear expression of Ki-67 was determined and both were compared between both groups. Results: The mean expression of Ki67 was 8.5% in the control group, and 34% in the melanoma group, which was statistically significant (p < 0.0001). Discussion: Ki67 expression in acral lentiginous melanomas is higher than in acral nevi. Prognostic value of Ki67 is still considered controversial. However, there are several studies where, in combination with other markers, their prognostic value is reinforced. Conclusions: Due to the wide gap in Ki67 expression between melanomas and nevi showed in this study, Ki67 expression, referred to as a proliferative index, could be considered as a prognostic factor even more objective than the mitotic index.