CDKN2A and melanoma: A number of novel candidate melanoma predisposition genes, in addition to the well know high penetrance genes such as Cyclin Dependent Kinase Inhibitor 2A (CDKN2A), Cyclin-Dependent Kinase 4 (CDK4) and low-penetrance genes such as Melanocortin 1 Receptor (MC1R) have been uncovered in the last few years.