STK11 and pancreatic intraductal papillary-mucinous neoplasm: KRAS mutation, the initiating event involved in PDAC tumorigenesis, is found in low grade PanIN lesions and can induce intraductal papillary mucinous neoplasm (IPMN) formation with inactivation of tumor suppressor genes such as LKB1 and PTEN synergistically (80–82).