Some studies distinguish eCCAs into perihilar (pCCA) and distal (dCCA)/ampullary carcinoma: pCCAs are characterized by frequent fusion events of the Protein Kinase A components and mitochondrial synthase, α subunit (ATP1B) determining MAPK activation, ELF3 mutations and ARID1B mutations [42]; dCCAs and ampullary carcinomas display many molecular abnormalities similar to dCCAs, with frequent mutations at the level of TP53, KRAS, APC, CTNNB1, SMAD4, ARID2, ELF3, GNAS, ERBB2 and ERBB3 genes [43,44]. Here, GNAS is linked to carcinoma of the ampulla of vater.