CDK4 and melanoma: Prevalence of other genetic alterations (RAS, TP53, CDKN2A, PREX2, and RASA2 mutations; CDKN2A and PTEN deletions, CCND1, MITF, and CDK4 amplifications) is higher in metastatic that in primary melanomas, most likely due to the expansion of cell subpopulations during tumor progression.