Bile duct cancer is a cancer that starts in the bile duct. In order to understand this cancer, it helps to know about the normal structure and function of the bile duct.

About the bile duct

The bile duct is a thin tube, about 4 to 5 inches long, that reaches from the liver to the small intestine. The major function of the bile duct is to transport a fluid called bile from the liver and gallbladder to the small intestine, where it helps digest the fats in foods.

Different parts of the bile duct system have different names. In the liver, it begins as many tiny tubes (ductules) where bile collects from the liver cells. The ductules come together to form small ducts, which then merge into larger ducts and eventually the left and right hepatic ducts. These ducts exit from the liver and join to form the common hepatic duct. About one third of the way along the length of the bile duct, the gallbladder (a small organ that stores bile) attaches by a small duct called the cystic duct. The combined duct is called the common bile duct. The common bile duct passes through part of the pancreas before it empties into the first part of the small intestine (the duodenum), next to where the pancreatic duct also enters the small intestine.

Types of bile duct cancers

Cancers can develop in any part of the bile duct and, based on their location, are divided into 3 groups. Cancers in these different areas may cause different symptoms.

Intrahepatic bile duct cancers: These cancers develop in the smaller bile duct branches inside the liver. They can sometimes be confused with cancers that start in the liver cells, which are called hepatocellular carcinomas, and are often treated the same way. Only about 1 out of 10 bile duct cancers are intrahepatic.

Hilar (also called perihilar) bile duct cancers: These cancers develop where the hepatic ducts have joined and are just leaving the liver. They are also called Klatskin tumors. These are the most common type of bile duct cancer.

Distal bile duct cancers: These bile duct cancers are found further down the bile duct, closer to the small intestine.

More than 95% of bile duct cancers are of the adenocarcinoma type. Adenocarcinomas are cancers of glandular cells that can develop in several organs of the body. Bile duct adenocarcinomas develop from the mucus glands that line the inside of the duct. Cholangiocarcinoma is another name for a bile duct adenocarcinoma.

Not all bile duct tumors are cancerous. Bile duct hamartomas and bile duct adenomas are benign (non-cancerous) tumors and, therefore, are not discussed further in this document.

Other cancers in the liver

Hepatocellular carcinomas, which develop from liver cells, are more common than cholangiocarcinomas of bile duct cells. Hepatocellular carcinoma is discussed in more detail in our document, Liver Cancer.

Adenocarcinomas that form in other organs, such as the pancreas, colon, rectum, stomach, lung, breast, or prostate, may spread to the liver. These are called secondary liver cancers or liver metastases. Their prognosis and treatment are not the same as hepatocellular carcinoma or cholangiocarcinoma, but instead depend on where the cancer started.