When you get a diagnosis of cancer, it's natural to wonder what may have caused the disease. Doctors can't always explain why one person gets liver cancer and another doesn't. However, we do know that people with certain risk factors may be more likely than others to develop liver cancer. A risk factor is something that may increase the chance of getting a disease.

Studies have found the following risk factors for liver cancer:

• Infection with hepatitis B virus (HBV) or hepatitis C virus (HCV): Liver cancer can develop after many years of infection with either of these viruses. Around the world, infection with HBV or HCV is the main cause of liver cancer.
  
  HBV and HCV can be passed from person to person through blood (such as by sharing needles) or sexual contact. An infant may catch these viruses from an infected mother. Although HBV and HCV infections are contagious diseases, liver cancer is not. You can't catch liver cancer from another person.
  
  HBV and HCV infections may not cause symptoms, but blood tests can show whether either virus is present. If so, the doctor may suggest treatment. Also, the doctor may discuss ways to avoid infecting other people.
  
  In people who are not already infected with HBV, hepatitis B vaccine can prevent HBV infection. Researchers are working to develop a vaccine to prevent HCV infection.
  
  
• Heavy alcohol use: Having more than two drinks of alcohol each day for many years increases the risk of liver cancer and certain other cancers. The risk increases with the amount of alcohol that a person drinks.
  
  
• Aflatoxin: Liver cancer can be caused by aflatoxin, a harmful substance made by certain types of mold. Aflatoxin can form on peanuts, corn, and other nuts and grains. In parts of Asia and Africa, levels of aflatoxin are high. However, the United States has safety measures limiting aflatoxin in the food supply.
  
  
• Iron storage disease: Liver cancer may develop among people with a disease that causes the body to store too much iron in the liver and other organs.
  
  
• Cirrhosis: Cirrhosis is a serious disease that develops when liver cells are damaged and replaced with scar tissue. Many exposures cause cirrhosis, including HBV or HCV infection, heavy alcohol use, too much iron stored in the liver, certain drugs, and certain parasites. Almost all cases of liver cancer in the United States occur in people who first had cirrhosis, usually resulting from hepatitis B or C infection, or from heavy alcohol use.
  
  
• Obesity and diabetes: Studies have shown that obesity and diabetes may be important risk factors for liver cancer.

The more risk factors a person has, the greater the chance that liver cancer will develop. However, many people with known risk factors for liver cancer don't develop the disease.

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