Holcombe et al. investigated samples from biliary tract cancers (126 extrahepatic cholangiocarcinomas, 434 intrahepatic cholangiocarcinomas, 244 gallbladder cancers, and 11 not specified) and identified high PD-1 expression in 40% of samples and high PD-L1 expression in 15% [105]. The gene discussed is CD274; the disease is biliary tract neoplasm.