​The liver is largest solid organ in the body and is essential for life. It is involved in many processes of the body, such as producing bile, essential proteins, nutrients and detoxification among others. Bile ducts within the liver join together to form one main bile duct, located just outside the liver (at the hilum), which carries bile to the small intestine. This main bile duct is called the common hepatic duct. The cystic duct joins the gallbladder to the common hepatic duct, and the combined duct is called the common bile duct. (Figure 1)

Cholangiocarcinoma (CCA) (Bile Duct Cancer) is next most common primary cancer of the liver, after hepatocellular carcinoma (HCC). It arises from cells lining the bile ducts (cholangiocytes).

They can occur within the liver (intrahepatic) or near the liver hilum (perihilar) or beyond the liver (extrahepatic or distal). Tumours involving the bile duct bifurcation (hilar) are also known as "Klatskin" tumours. Although they are rare, these cancers are highly lethal because most are locally advanced at presentation.