Cholangiocarcinoma starts in the bile duct, 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.
Cancers can develop in any part of the bile duct and, based on their location, are classified into 3 types:
- Intrahepatic cholangiocarcinoma
- Perihilar cholangiocarcinoma
- Distal cholangiocarcinoma.
Cancers in these different areas may cause different symptoms.
What is Intrahepatic Cholangiocarcinoma?
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. Only 10% of bile duct cancers are intrahepatic.
What is Perihilar (Hilar) Cholangiocarcinoma?
These cancers develop where the right and left hepatic ducts have joined and are leaving the liver. They are also called Klatskin tumors. These are the most common type of cholangiocarcinoma accounting for more than half of all bile duct cancers.
What is Distal Cholangiocarcinoma?
These cancers are found further down the bile duct closer to the small intestine. Distal bile duct cancers start outside the liver and make up 20 to 30% of bile duct cancers.
What is Extrahepatic Cholangiocarcinoma?
Because perihilar and distal bile duct cancers start outside the liver, they are often grouped together and referred to as extrahepatic cholangiocarcinoma.
Cholangiocarcinoma 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.
Adapted from National Institutes of Health: http://www.cancer.gov/