Connecting the liver, small intestine and gallbladder, bile ducts are defined as a network of tubes which starts in the liver, where they collect bile produced by the organ (to aid the digestion of foods). A number of small ducts make up the system, with some coming together to become both the right and left hepatic ducts. These two bile ducts joined together at the outside of the liver and form what is known as the common hepatic duct.
The common hepatic duct is connected to the gallbladder using the cystic duct, through which bile passes to be stored in the gallbladder. This bile, now stored in the gallbladder, is released through the cystic duct and into the small intestine when food is digested.
Bile duct cancer (otherwise known as cholangiocarcinoma) occurs when malignant cells (known as cancer cells) form within any of the bile ducts in the system.
The first type of bile duct cancer is known as intrahepatic cholangiocarcinoma and is defined by the presence of cancer cells within the bile ducts that are located inside the liver. Intrahepatic cholangiocarcinomas are a relatively rare form of bile duct cancer and only occur as a small percentage of all bile duct cancers.
The second form of bile duct cancer, known as extrahepatic bile duct cancer, is cancer which is formed outside of the liver, within the extrahepatic bile ducts. The extrahepatic bile ducts have two separate regions, the distal region, and the hilum region. When Extrahepatic bile duct cancer is present, it can form in either one of these two systems.
- The form of bile duct cancer which is found within the hilum region of the extrahepatic bile duct is referred to as either perihilar cholangiocarcinoma or a Klatskin tumor. This is the area where two small bile ducts to the left and right of the liver join together and become the common hepatic duct.
- The form of cancer found in the distal region (comprising of the common bile duct through the pancreas and small intestine) is called extrahepatic cholangiocarcinoma.
There are several preexisting conditions and diseases that can increase the risk of developing bile duct cancer. These risk factors simply increase the likelihood of developing malignant cells and do not mean that cancer is certain. Anyone can develop cancer, so the absence of all known risk factors doesn't mean that a person will not suffer from the condition. If you have any of the risk factors, or you are worried about certain symptoms, you should speak with your doctor as soon as possible.
One of the risks factors is a disease known as primary sclerosing cholangitis; this is a progressive disease (meaning it will get gradually worse over time) which causes the bile ducts to be blocked due to scarring or inflammation. Another possible risk factor is seen in those suffering from Chronic ulcerative colitis. Chronic ulcerative colitis occurs when cysts form within the bile ducts, blocking the flow of bile through the system and resulting in swelling and possible infection. Although rare, those who have been previously, or are currently, infected with a Chinese liver fluke parasite are at a greater risk of developing bile duct cancer.
The stages of cancer refer to the way medical cancer professionals measure the extent of the malignant cancer cells. The most common system used in cancer staging is known as the American Joint Committee on Cancer (AJCC) TNM system, with three different staging systems for bile duct cancer, dependent on where the malignant cells first appear.
The three staging systems, and three different areas where a cancer can begin, are broken up by distinct region. Cancers that start within the liver (also known as Intrahepatic bile duct cancer), cancers that begin just outside the liver, in the hilum region (also known as perihilar bile duct cancer) and cancers which begin further down the bile duct system, in the distal region (also known as distal bile duct cancer) make up the three regions.
Bile duct cancers almost always begin in the internal wall layers of the bile duct and can grow and spread through these walls and into blood vessels, other organs, lymph nodes and throughout the body using the circulatory and lymphatic systems.
The TNM system used by most cancer professionals is made up of three separate ratings that define a separate piece of information relating to cancer.
The T stands for the main tumor and has number or letters after it to indicate whether cancer has spread beyond the wall of the bile duct and to what extent this has happened.
The N tells us whether or not cancer has spread to any lymph nodes that may be nearby to the main tumor or cell cluster.
The M tells us if cancer has metastasized within the body to other organs.
These three stages will indicate to what level cancer has spread and how treatable cancer may be.