What Is Bile Duct Cancer?
Cancer starts when cells in the body begin 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 normal bile ducts and what they do.
About the bile ducts
The bile ducts are a series of thin tubes that reach from the liver to the small intestine. The major function of the bile ducts 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 (called 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. All of these ducts within the liver are called intrahepatic bile ducts.
The left and right hepatic ducts exit from 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) joins the common hepatic duct through 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 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
Cancers can develop in any part of the bile duct system and, based on their location (see picture below), 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 can 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 hepatocellularcarcinomas, and are often treated the same way.
Perihilar (also called hilar) bile duct cancers
These cancers develop 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 are called cholangiocarcinomas. Most of these are adenocarcinomas, which are cancers that start in glandular cells. Bile duct adenocarcinomas develop from the mucous gland cells that line the inside of the duct.
Other types of bile duct cancers are much less common. These include sarcomas, lymphomas, and small cell cancers. The information here does not cover these other types of bile duct cancer.
The rest of this information refers only to cholangiocarcinomas.
Benign bile duct tumors
Not all bile duct tumors are cancerous. Bile duct hamartomas and bile duct adenomas are examples of benign (non-cancerous) tumors, which aren’t discussed further in this document.
Other cancers in the liver
The most common type of cancer that starts in the liver – much more common than intrahepatic bile duct cancer – is hepatocellular carcinoma, which develops from liver cells. Hepatocellular carcinoma is discussed in more detail in Liver Cancer.
Cancers that start in some other organs can spread to the liver. These are called secondaryliver 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’s important to know whether an adenocarcinoma in the liver started in bile ducts (and is a cholangiocarcinoma), or whether it started in another organ (such as the colon) and then spread to the liver.