What is bile duct cancer?
Bile duct cancer 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 move a fluid called bile from the liver and gallbladder to the small intestine, where it helps digest the fats in food.
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. The ducts within the liver are called intrahepatic bile ducts. These ducts exit from the liver and join to form the common hepatic duct at the hilum. 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 (see picture), are classified into 3 types:
- Intrahepatic bile duct cancers
- Perihilar (also called hilar) bile duct cancers
- Distal bile duct cancers
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 in 10 bile duct cancers are intrahepatic.
Perihilar (also called hilar) bile duct cancers
These cancers develop at the hilum, 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, making up 6 or 7 of every 10 bile duct cancers. These cancers are grouped with distal bile duct cancers as extrahepatic bile duct cancers.
Distal bile duct cancers
These bile duct cancers are found further down the bile duct, closer to the small intestine. Because these bile ducts are outside of the liver, these cancers are grouped with perihilar cancers as extrahepatic bile duct cancers. Distal bile duct cancers make up 2 to 3 of every 10 bile duct cancers.
Histologic types of bile duct cancer
Bile duct cancers can also be divided into types based on how the cancer cells look under the microscope. More than 95% of bile duct cancers are carcinomas and most are adenocarcinomas. Adenocarcinomas are cancers of glandular cells that can develop in several organs of the body. Bile duct adenocarcinomas develop from the mucous glands that line the inside of the duct. Cholangiocarcinoma is another name for a bile duct carcinoma. Other types of bile duct cancers are much more rare. These include sarcomas, lymphomas, and small cell cancers. This document does not discuss these other types of bile duct cancer, and uses the term bile duct cancer to mean cholangiocarcinoma.
Not all bile duct tumors are cancerous. Bile duct hamartomas and bile duct adenomas are benign (non-cancerous) tumors, which is why they aren’t discussed further in this document.
Other cancers in the liver
Hepatocellular carcinomas develop from liver cells and are more common than cholangiocarcinomas of bile duct cells. Hepatocellular carcinoma is discussed in more detail in our document, Liver Cancer.
Cancers that start in other organs may spread to the liver. These are called secondary liver cancers or liver metastases. Their outlook and treatment are not the same as cancer that starts in the liver (such as hepatocellular carcinoma) or bile ducts (like cholangiocarcinoma), but instead depend on where the cancer started. For this reason, it is important to know whether an adenocarcinoma in the liver started in bile ducts (and is a cholangiocarcinoma), or whether it started in other organs like the pancreas, colon, rectum, stomach, lung, breast, or prostate and then spread to the liver.
Last Medical Review: 10/30/2013
Last Revised: 10/30/2013