What Is Bile Duct Cancer

What Is Bile Duct Cancer?
Cancer starts when cells in the body start to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?

Bile duct cancer starts in a bile duct. To understand this cancer, it helps to know about the bile ducts and what they normally do.

About the bile ducts

color illustration of the digestive system which shows the location of the esophagus, stomach, pancreas, rectum, colon, small intestine, gallbladder and liver
The bile ducts are a series of thin tubes that go from the liver to the small intestine. Their major job is to move a fluid called bile from the liver and gallbladder into the small intestine, where it helps digest the fats in food.


illustration showing the location of the common bile duct, liver, pancreas, pancreatic duct, ampula of vater, duodenum, gallbladder, cystic duct, right hepatic duct, left hepatic duct and common hepatic duct
Different parts of the bile duct system have different names. In the liver it begins as many tiny tubes (called ductules) where bile collects from the liver cells. The ductules come together to form tubes called small ducts. These merge into larger ducts and then the left and right hepatic ducts. All of these ducts within the liver are called intrahepatic bile ducts.

The left and right hepatic ducts exit the liver and join to form the common hepatic duct in an area called the hilum. Lower down, the gallbladder (a small organ that stores bile) is joined to the common hepatic duct by a small duct called the cystic duct. This combined duct is called the common bile duct. The common bile duct passes through part of the pancreas before it joins with the pancreatic duct and empties into the first part of the small intestine (the duodenum) at the ampulla of Vater.

Types of bile duct cancers by location
Cancer can start in any part of the bile duct system. Based on where the cancers are (see the picture below), they're grouped into 3 types:

Intrahepatic bile duct cancers
Perihilar (also called hilar) bile duct cancers
Distal bile duct cancers
Another name for bile duct cancer is cholangiocarcinoma.


illustration showing the location of the common bile duct, intrahepatic bile ducts, perihilar bile ducts and distal bile ducts in relation to the liver, pancreas, gallbladder and duodenum (intestine)
Cholangiocarcinomas in these different groups cause different symptoms.

Intrahepatic bile duct cancers
These cancers start in the smaller bile duct branches inside the liver. Sometimes they're confused with cancers that start in the liver cells, which are called hepatocellular carcinomas , which are often treated the same way.

Perihilar (also called hilar) bile duct cancers
These cancers start at the hilum, where the left and right hepatic ducts have joined and are just leaving the liver. These are also called Klatskin tumors. These cancers are grouped with distal bile duct cancers as extrahepatic bile duct cancers.

Distal bile duct cancers
These cancers are found further down the bile duct, closer to the small intestine. Like perihilar cancers, these are extrahepatic bile duct cancers because they start outside of the liver.

Types of bile duct cancer by cell type
Bile duct cancers can also be divided into types based on how the cancer cells look under the microscope.

Nearly all bile duct cancers or cholangiocarcinomas are adenocarcinomas, which are cancers that start in glandular cells. Bile duct adenocarcinomas start in the mucous gland cells that line the inside of the ducts.

Other types of bile duct cancers are much less common. These include sarcomas, lymphomas, and small cell cancers. Our information does not cover these other types of bile duct cancer.

Benign bile duct tumors
Not all bile duct tumors are cancer. Bile duct hamartomas and bile duct adenomas are examples of benign (non-cancer) tumors.

Other cancers in the liver
The most common type of cancer that starts in the liver – much more common than cholangiosarcoma – is hepatocellular carcinoma, which starts in cells that form the liver.

Cancers that start in other organs can spread to the liver. These are called liver metastases or metastatic cancer to the liver. 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’s important to know whether a tumor in the liver started in bile ducts (is a cholangiocarcinoma), or whether it's made up of cancer cells that started in another organ (like the colon) and spread to the liver (is metastatic cancer).

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