The most common place for a tumour to grow is in the lining of the duct wall, where the hepatic ducts join the common bile duct. This is called a Klatskin tumour. The cancer can also grow in the part of the hepatic bile duct that is outside the liver (the extrahepatic bile duct).

Bile duct tumours can also start in the liver itself.

The place where the cancer first starts to grow is called the primary site.