“…Data from previous studies on familial melanoma [20,21] also indicating that the penetrance varies with melanoma population incidence rates [9] are consistent with this hypothesis. In fact, either the standardized incidence rates of melanoma (roughly, 12 cases per 100, 000 inhabitants in northern Italy versus four cases per 100.000 inhabitants in southern Italy [1]) or the prevalence of familial MM cases (9.2% in patients from northern Italy [19,21] v 4.7% in those from southern Italy in this study) are significantly different in these two geographic areas. Thus, the same factors that affect population incidence of MM may also mediate CDKN2A penetrance.…”