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?
Only cancers that start in the liver are called liver cancer (primary liver cancer). To understand liver cancer, it helps to know about the normal structure and function of the liver.
About the liver
The liver is the largest internal organ. It lies under your right ribs just beneath your right lung. It is divided into lobes.
You cannot live without your liver. It has several important functions:
The liver is made up mainly of cells called hepatocytes. It also is made up of other types of cells, including cells that line its blood vessels and cells that line small tubes in the liver called bile ducts. The bile ducts extend out of the liver and carry bile from the liver to the gallbladder or directly to the intestines.
These different types of cells in the liver can form several types of malignant (cancerous) and benign (non-cancerous) tumors. These tumors have different causes, are treated differently, and have a different prognosis (outlook).
Benign liver tumors
Benign tumors sometimes grow large enough to cause problems, but they do not grow into nearby tissues or spread to distant parts of the body. If they need to be treated, the patient can usually be cured with surgery.
The most common type of benign liver tumor, hemangiomas, start in blood vessels. Most hemangiomas of the liver cause no symptoms and do not need treatment. But some may bleed and need to be removed surgically.
Hepatic adenoma is a benign tumor that starts from hepatocytes (the main type of liver cell). Most cause no symptoms and do not need treatment. But some eventually cause symptoms, such as pain or a mass in the abdomen (stomach area) or blood loss. Because there is a risk that the tumor could rupture (leading to severe blood loss) and a small risk that it could eventually develop into liver cancer, most experts will usually advise surgery to remove the tumor if possible.
Using certain drugs may increase the risk of getting these tumors. Women have a higher chance of having one of these tumors if they take birth control pills, although this is rare. Men who use anabolic steroids may also develop these tumors. Adenomas may shrink when the drugs are stopped.
Focal nodular hyperplasia
Focal nodular hyperplasia (FNH) is a tumor-like growth made up of several cell types (hepatocytes, bile duct cells, and connective tissue cells). Although FNH tumors are benign, it can be hard to tell them apart from true liver cancers, and doctors sometimes remove them when the diagnosis is unclear. If you have symptoms from an FNH tumor, it can be removed with surgery.
Both hepatic adenomas and FNH tumors are more common in women than in men.
Types of primary liver cancer
A cancer that starts in the liver is called primary liver cancer. There is more than one kind of primary liver cancer.
Hepatocellular carcinoma (hepatocellular cancer)
This is the most common form of liver cancer in adults. .
Hepatocellular cancer (HCC) can have different growth patterns:
Using a microscope, doctors can distinguish several subtypes of HCC. Most often these subtypes do not affect treatment or prognosis (outlook). But one of these subtypes, fibrolamellar, is important to recognize. This type is rare, making up less than 1% of HCCs. This type is most often seen in women younger than age 35, and often the rest of the liver is not diseased. This subtype generally has a better outlook than other forms of HCC.
Here “liver cancer” is hepatocellular carcinoma.
Intrahepatic cholangiocarcinoma (bile duct cancer)
About 10% to 20% of cancers that start in the liver are intrahepatic cholangiocarcinomas. These cancers start in the cells that line the small bile ducts (tubes that carry bile to the gallbladder) within the liver. (Most cholangiocarcinomas actually start in the bile ducts outside the liver.)
Although the rest of this document deals mainly with hepatocellular cancers, cholangiocarcinomas are often treated the same way. For more detailed information on this type of cancer, see our document, Bile Duct (Cholangiocarcinoma) Cancer.
Angiosarcoma and hemangiosarcoma
These are rare cancers that begin in cells lining the blood vessels of the liver. People who have been exposed to vinyl chloride or to thorium dioxide (Thorotrast) are more likely to develop these cancers. See the section "Liver cancer risk factors" Some other cases are thought to be caused by exposure to arsenic or radium, or to an inherited condition known as hereditary hemochromatosis. In about half of all cases, no likely cause can be identified.
These tumors grow quickly and are usually too widespread to be removed surgically by the time they are found. Chemotherapy and radiation therapy may help slow the disease, but these cancers are usually very hard to treat. These cancers are treated like other sarcomas. For more information, see our document Sarcoma – Adult Soft Tissue Cancer.
This is a very rare kind of cancer that develops in children, usually in those younger than 4 years old. The cells of hepatoblastoma are similar to fetal liver cells. About 2 out of 3 children with these tumors are treated successfully with surgery and chemotherapy, although the tumors are harder to treat if they have spread outside the liver.
Secondary liver cancer (metastatic liver cancer)
Most of the time when cancer is found in the liver it did not start there but has spread (metastasized) from somewhere else in the body, such as the pancreas, colon, stomach, breast, or lung. Because this cancer has spread from its original (primary) site, it is a secondary liver cancer. These tumors are named and treated based on their primary site (where they started). For example, cancer that started in the lung and spread to the liver is called lung cancer with spread to the liver, not liver cancer, and it is treated as lung cancer.
In the United States and Europe, secondary (metastatic) liver tumors are more common than primary liver cancer. The opposite is true for many areas of Asia and Africa.
For more information on liver metastases from different types of cancer, see our documents on specific cancer types, as well as our document, Advanced Cancer.
Most of the remaining content refers only to hepatocellular carcinoma.
Last Revised: 04/28/2016