The major function of the bile
duct is to transport bile to the small intestine where it
aids in digesting food. The bile duct is a thin tube, about 4 to 5
inches long, that reaches from the liver to the small intestine. In the
liver, it begins as many small channels that gather bile from the liver
cells. These all join into one tube or duct (this part of
the bile duct is called the hepatic
duct). About one third of the way along the length of the
bile duct, the gallbladder
attaches by a small duct called the cystic
duct. The combined duct is called the common bile duct.
The end of this part of the bile duct empties into the earliest part of
the small intestine, 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 divided into 3 groups. About half of the cancers develop
in the smaller bile duct branches inside the liver and are called
intrahepatic
(inside the liver) bile duct cancers. These can be
confused with cancers that start in the liver cells and are called
hepatic carcinomas.
It is possible to tell these 2 types of tumors
apart by looking at them under a microscope.
The next most common type
of bile duct cancers is found in the common bile duct nearest the
intestine. Doctors call these distal
bile duct cancers.
The least
common type is bile duct cancer that develops at the part of the
hepatic duct where the bile ducts have joined and are just leaving the
liver. Cancers that develop here are called perihilar cancers,
or
sometimes Klatskin tumors
(named after the doctor who described them).
Cancers beginning in these 3 different areas may cause different
symptoms.
More than 95% of bile duct cancers are of the adenocarcinoma type.
Adenocarcinomas are cancers of glandular cells that can develop in
several organs of the body. Bile duct adenocarcinomas develop from the
mucus glands that line the inside of the duct. Cholangiocarcinoma
is another name for a bile duct adenocarcinoma. Today, most doctors use
this term for all bile duct adenocarcinomas. In the past, doctors used
this term only in describing intrahepatic or perihilar tumors, but not
distal bile duct cancers.
Not all bile duct tumors are cancerous. Bile duct hamartomas and bile
duct adenomas
are benign (non-cancerous) tumors and, therefore, are not discussed
further in this document. Hepatocellular
carcinomas, which develop from liver cells, are more
common than cholangiocarcinomas of bile duct cells. Hepatocellular
carcinoma is discussed in more detail in the American Cancer Society
document, Liver
Cancer.
Adenocarcinomas that form in other organs, such as the pancreas, colon,
rectum, stomach, lung, breast, or prostate, may spread through the
bloodstream to the liver. These are called secondary liver cancers or
liver metastases. Their prognosis and treatment are not the same as
cholangiocarcinomas, and depend on where the cancer started.
Revised: 04/17/2006
|
