What is cholangiocarcinoma (bile duct cancer)?
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?
Intrahepatic CCA occurs inside the liver where cancer develops in the hepatic bile ducts or the smaller intrahepatic biliary ducts. In some cases, patients express a combined diagnosis.
What is Perihilar (Hilar or Klatskin Tumor) Cholangiocarcinoma?
These cancers develop where the right and left hepatic ducts have joined and are leaving the liver. These are the most common type of cholangiocarcinoma accounting for more than half of all bile duct cancers.
What is Distal Cholangiocarcinoma?
Distal CCA occurs outside the liver after the right and left hepatic bile ducts have joined to form the common bile duct. This type of cancer is found where the common bile duct passes through the pancreas and into the small intestine.
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.nih.gov/
Why is cholangiocarcinoma considered a rare cancer?
About Rare Cancers
Rare cancers are those that affect fewer than 40,000 people per year in the U.S. As a group, they make up just over a quarter of all cancers. Because rates of cancer in children are very low, all children’s cancers are considered rare. A quarter of all cancer deaths each year are due to rare cancers. Although new treatments are always being developed, finding new treatments for rare cancers can be difficult for many reasons.
Why are rare cancers challenging?
Rare cancers are challenging for patients, doctors, and scientists.
- It often takes a long time from the time you think something is wrong to the time when doctors know that you have a rare cancer and what kind of cancer it is.
- It is hard to find doctors who know a lot about your cancer and how to treat it.
- It is hard to know what to do when doctors don’t agree on how to treat your cancer.
- You may need to travel far from your home and family to get treatment for your rare cancer.
- You may not know what to tell your patient about what to expect with their rare cancer.
- You may not have been trained in how to treat this type of rare cancer.
- It is hard to find an expert in the rare cancer who can answer questions or to whom you can refer your patient.
- There may be no information about the rare cancer to give you ideas on which drugs could treat it.
- There may be no animal or cell models of the rare cancer in which to test your ideas.
- There may not be enough tumor samples from rare cancer patients available for your research.
- If you have an idea of a drug that could treat the cancer, it may be hard to find enough patients with the rare cancer to test your idea.
Adapted from cancer.gov