CDKN2A and pachyonychia congenita: For example, K-Ras, cyclin-dependent kinase inhibitor 2A (CDKN2A), growth factor receptors (EGFR, FGFR, IGFR), transforming growth factor-beta (TGF-β), p53, Wnt (Wingless and Int-1), Notch, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and Hedgehog, etc. are some of the major signaling pathways that are altered during PC progression [12,13,14,15].