Cancer found in the liver is not always "liver cancer" often, the liver is just the organ to which the cancer has spread from another place.
The term primary liver cancer distinguishes cancer that begins in the liver from a malignancy that starts elsewhere and metastasizes to the liver; thats called secondary liver cancer. For example, when the cancer starts in the lung and metastasizes to the liver, it is called metastatic lung cancer, even though a tumor is found in the liver.
Primary liver cancers are rare: Secondary liver cancer accounts for more than 90 percent of tumors in the liver, according to Tusar Desai, MD, a gastroenterologist and hepatologist (liver expert) at Beaumont Hospital in Royal Oak, Mich.
"Part of the liver's job is to filter out toxins in the blood, so you can imagine if there are cancer cells floating through the body, they are going to be deposited in the liver," Dr. Desai says.
Liver Cancer: Some Statistics
Though rare, primary liver cancer is still an efficient killer: In the United States, liver cancer ranks as the fifth most common cause of cancer death in men, the ninth in women.
As for new cases, the American Cancer Society estimated that there were 21,370 people diagnosed with liver cancer in 2008, and that some 18,410 people died from the disease.
Liver cancer is not a disease of the young. It strikes older people more, with 90 percent of cases occurring in people 45 years old or older.
Liver Cancer: Who Gets It
Liver cancer rates are about twice as high in African-Americans, Hispanics, Asian-Americans, and Pacific Islanders as in whites. Most conspicuously, liver cancer strikes far more men than women. In 2008, 71 percent of new cases were in men.
One theory behind the higher incidence of liver cancer in men is that men produce more of the protein interleukin-6 (IL-6) in response to an injury in the liver. In women, estrogen inhibits secretion of IL-6, which is a key biochemical in the process of chronic inflammation that can lead to cancer. The effect has been directly observed in experiments with mice.
Certain factors can increase a person's risk of liver cancer, including being infected with hepatitis B or C or having cirrhosis.
Liver Cancer: Hepatocellular Carcinoma
There are different kinds of liver cancer, depending on the cells in which it begins.
Also called hepatoma, hepatocellular carcinoma accounts for three-fourths of all liver cancers. It starts in the hepatocytes, the cells that make up most of the liver. Hepatocellular cancers occur in two forms:
Liver Cancer: Intrahepatic Cholangiocarcinomas
This liver cancer originates in the ducts that carry bile a liquid that takes fatty acids and breaks them down mdash; to the gallbladder. The tumor may occur in the liver itself or, more often, in the duct outside the liver. This cancer accounts for 10 percent to 20 percent of liver cancers.
Liver Cancer: Hemangiosarcomas and Angiosarcomas
These are rare, fast-growing cancers that start in the liver blood vessels and are believed linked to an inherited condition known as hemochromatosis. They also may be caused by exposure to toxic chemicals, such as vinyl chloride, thorium dioxide, or arsenic compounds. The disease may be slowed by chemotherapy and radiation, but most patients only survive a year after diagnosis.
Liver Cancer: Hepatoblastoma
This is a rare form of cancer that occurs in children 4 years old and younger. In about 70 percent of cases, a child with this disease can be treated successfully; the survival for early-stage hepatoblastoma is more than 90 percent.
Benign Liver Tumors
Benign (non-cancerous) tumors also can occur in the liver, but these do not spread and often do not cause symptoms or need treatment. However, when a benign tumor causes bleeding, or abdominal pain, or there is a risk that the tumor could rupture, surgery may be needed.