Carcinoma of the gallbladder (GBC) is the most common and aggressive form of biliary tract cancer (BTC) usually arising in the fundus of the gallbladder, rapidly metastasizing to lymph nodes and distant sites. The disease is Monarch Disease Ontology entry MONDO_0018918 (carcinoma of gallbladder and extrahepatic biliary tract). Also known as: carcinoma of gallbladder and EBT.