GNAS and pancreatic intraductal papillary-mucinous neoplasm: Recent investigations of IOPN have reported that KRAS, GNAS, and RNF43 mutations, which are frequently observed in IPMN, are rare, while PRKACA and PRKACB fusion genes and gene mutations in ARHGAP26, ASXL1, EPHA8, and ERBB4, which are not observed in IPMN, have been detected [6–11].