Another point of view about the expression of p16 and Ki67 in melanocytic and non-melanocytic cutaneous lesions

The new analysis on the expression of cell cycle regulators, (used in various neoplasms) and the nominal immunohistological essays, still represent valid and feasible diagnostic methods in most pathology practice. We examined 114 paraffin-embedded histological specimens of melanocytic cutaneous lesions. The primary objective of this study was to explore the potential diagnostic of two important cell cycle regulators (p16 and Ki67) evaluating also the variations of expression using a semi quantitative graded scale. While, another aim was to study an hypothetical correlation between p16 expression (in melanocytic and non-melanocytic lesions) and two independent variables, such as the age of the patients and the anatomical sites ( if sun exposed or not sun exposed) of the lesions analyzed. Cell population was considered positive for antibody-specific p16 and Ki67 when at least 33 % of the cells showed well defined nuclear and/or cytoplasmic staining. A special p16 and Ki67 trend was found only in Spitz nevus (SN), atypical Spitz nevus (ASN) and invasive malignant melanoma (MM) . While, regarding the other lesions ( junctional melanocytic nevus, in situ MM, superficial spreading MM, non-melanoma cancers) discriminative values were not found. P16 was over expressed on sun exposed sites and was hypo expressed on non-sun-exposed areas , founding a statistical significance correlation ( p < 0.03); while, p16 expression was over expressed in patients ≥ 61 while it was hypo expressed in patients ≤ 60 ( p = 0.09).