BRCA1 and biliary tract cancer: In contrast to pancreatic cancer, it is unclear whether BRCA1/2 germline mutation is responsible for the risk of developing biliary tract cancer, but it has been reported that BRCA1 or BRCA2 germline mutations increase the relative risk of biliary tract cancer by 1.87-fold (0.59 to 5.88) and 4.97-fold (1.50−16.52), respectively [36,37].