Prognostic prediction of the immunohistochemical expression of p16 and p53 in cutaneous melanoma: a comparison of two populations from different geographical regions

p16INK4a and p53 are tumor-suppressor genes frequently altered in various malignancies, including cutaneous melanoma. The purpose of the study was to establish the prognostic value of immunohistochemical expression of p16INK4a and p53 in sporadic cutaneous melanoma (CM) in two regions with a high-risk for melanoma in Italy and Ecuador. Immunohistochemical staining of p16 and p53 was performed in samples of primary CM from 82 patients with Stage I and II melanoma according to the American Joint Committee on Cancer (AJCC) staging system. Survival differences between categories of p16 or p53 expression were analyzed using the product-limit procedure (Kaplan-Meier method, log-rank test). Clinical variables (gender, age, tumor location, Clark’s level, thickness) were correlated with survival and p16 or p53 expression. p16 nuclear immunoreactivity was observed in 85% of Italian patients compared to 48.7% of Ecuadorians; a small number of cases showed p53 immunoreactivity in both populations. Only nuclear p16 expression exhibited a significant correlation with survival (Italians p=0.001, Ecuadorians p=0.017) but did not appear to correlate with any clinicopathological parameter. No significant difference was observed in survival with regard to p53 expression or cytoplasmic p16. Our results demonstrate that nuclear expression of p16 can be considered a molecular prognostic factor in patients with sporadic CM and indicate its importance as a clinical marker.