CDKN2A and melanoma: The hypermethylation of specific tumor suppressor gene promoters has been described in melanoma and prevalently affects those genes involved in the cell cycle regulation, intracellular signalling, and apoptosis, including phosphatase and tensin homolog (PTEN), retinoic acid receptor (RAR)-β2, and cyclin-dependent kinase Inhibitor 2A (CDKN2A) [46,48].