Extrahepatic bile duct cancer is a rare disease in which malignant (cancer) cells form in the part of bile duct that is outside the liver.
A network of bile ducts (tubes) connects the liver and the gallbladder to the small intestine. This network begins in the liver where many small ducts collect bile, a fluid made by the liver to break down fats during digestion. The small ducts come together to form the right and left hepatic bile ducts, which lead out of the liver. The two ducts join outside the liver to become the common hepatic duct. The part of the common hepatic duct that is outside the liver is called the extrahepatic bile duct. The extrahepatic bile duct is joined by a duct from the gallbladder (which stores bile) to form the common bile duct. Bile is released from the gallbladder through the common bile duct into the small intestine when food is being digested.
Having colitis or certain liver diseases can increase the risk of developing extrahepatic bile duct cancer.