PBRM1 and gallbladder cancer: PBRM1 mutation frequencies were detected at the highest frequencies in intrahepatic BTC (9.9%, n = 103/1045; IHBCs) followed by gallbladder cancer (6.0%, n = 29/484) and extrahepatic BTC (4.5%, n = 11/244, EHBCs, Fig. 1b).