The liver is the largest organ in the body, located below the right lung. The liver is divided into right and left lobes. It is composed of hepatocytes, cells that process nutrients in the blood.
The liver’s main functions include absorbing nutrients from the blood and making bile, a fluid that helps digest fats. The liver breaks down and stores many of the nutrients absorbed from the intestine and helps remove toxic wastes from the body. In addition, the liver produces certain proteins that help stop bleeding from a cut or injury.
Unlike most other organs, the liver gets blood from two sources: the hepatic artery, which supplies the liver with oxygen-rich blood, and the portal vein, which carries nutrient-rich blood from the intestines to the liver.
Primary Liver Cancer: Hepatocellular Carcinoma
Primary liver cancer is relatively rare in the United States. The most common type of primary liver cancer in adults is hepatocellular carcinoma, which begins in liver cells called hepatocytes. Each year, approximately 16,000 Americans develop hepatocellular carcinoma. Hepatocellular carcinoma can begin as a single tumor that grows larger and eventually spreads beyond the liver. Patients with cirrhosis may develop several liver tumors.
The term “primary” means that the cancer begins in the liver. Most liver tumors start elsewhere in the body, such as in the colon or rectum, and spread (metastasize) to the liver.
In the United States, most patients with primary liver cancer have underlying liver disease related to alcohol intake, hepatitis (B or C), or a metabolic abnormality that affects the liver.
Primary liver cancer is much more common in developing countries throughout sub-Saharan Africa and Southeast Asia, largely due to the widespread prevalence of hepatitis B. Unfortunately, there are often no symptoms in the early stages of the disease, making liver cancer difficult to diagnose until it is advanced.
For information about the risk factors of developing liver cancer, visit that section of this information overview.
Other Types of Liver Cancer
Other types of liver cancer that are less common include:
- Fibrolamellar Carcinoma
A rare subtype of hepatocellular carcinoma, fibrolamellar carcinoma is less aggressive than other types of primary liver cancer and most often appears in younger patients. Fibrolamellar hepatocellular carcinoma is often confused with a type of benign liver tumor called focal nodular hyperplasia. Memorial Sloan-Kettering is one of the few centers in the United States with experience treating this type of liver cancer.
- Angiosarcomas, Hemangiosarcomas, and Hemangioendotheliomas
These fast-growing tumors arise in the blood vessels of the liver.
This type of tumor is a highly curable form of liver cancer that occurs mainly in very young children.
Find out more about cancer of the bile ducts within the liver in our gallbladder and bile duct cancers section. Find out more about secondary liver cancer in our overview of liver metastases.
Benign Liver Tumors
Several benign, or noncancerous, tumors also can form in the liver. Many do not cause symptoms and are only discovered when imaging tests are performed for another health condition. Benign liver tumors may not require treatment unless they cause bleeding or abdominal pain. The most common benign liver tumors include:
- Hepatic Adenomas
This type of benign tumor begins in the hepatocytes and occurs mainly in women of childbearing age. These precancerous tumors can rupture and bleed.
- Focal Nodular Hyperplasia
Focal nodular hyperplasia is a benign malformation of the liver that occurs mainly in women between the ages of 20 and 30 years. These tumors can be difficult to distinguish from cancerous liver tumors, but rarely require surgery.
An abnormal mass of blood vessels, hemangiomas are the most common type of benign liver tumor. Hemangiomas occur in up to 5 percent of adults, more often women. This type of liver tumor rarely causes pain or other problems.
- Liver Cysts
An estimated 5 percent of the population develops liver cysts — benign growths that contain fluid produced by the cell wall of the cyst. Most cysts do not need therapy.
Many patients with primary liver cancer have no symptoms. If symptoms occur, they may include:
- jaundice (a condition in which the skin and the whites of the eyes become yellow, urine darkens, and the color of stool becomes lighter than normal)
- general feeling of poor health or weakness
- loss of appetite
- weight loss
- swelling of the legs
- abdominal pain or discomfort