Intestinal IPNB belonging to type 2: Intestinal IPNB arising in the extrahepatic bile duct and belonging to type 2 did not harbor GNAS mutations but did show mutations in SMAD4, PIK3CA, APC and CTNNB1 [135], suggesting the different genetic changes from IPMN [136] and the above-mentioned intestinal IPNB belonging to type 1.Yang et al. also reported such intestinal IPNB belonging to type 2 with mucin hypersecretion and positive MUC2 different from intestinal IPNB with GNAS mutation and also from CTNNB1 mutated non-intestinal IPNB (see below) as an another category of IPNB [130]. The gene discussed is GNAS; the disease is pancreatic intraductal papillary-mucinous neoplasm.