KRAS and pachyonychia congenita: Previous studies of pancreatic tumorigenesis have suggested that mutations in PC driver genes occur in a specific order; activating mutations in KRAS are present in low-grade pancreatic intraepithelial neoplasia (PanIN-1) lesions4 (94.1% mutation rate5), and inactivating mutations in CDKN2A (17.0%), TP53 (63.9%) and SMAD4 (20.8%) occur thereafter and are found in transformed PanIN-2 and PanIN-3 lesions6,7.