The American Cancer Society (ACS) reports that hepatocellular carcinoma is the most frequent type of liver cancer and accounts for 3 out of 4 liver cancers. This type of liver cancer originates in the primary cell of the liver, which is the hepatocyte. Other more rare types of liver cancer include cholangiocarcinomas, which originate in the bile ducts; angiosarcomas and hemangiosarcomas, which originate in blood vessels in the liver; and hepatoblastomas, which occur infrequently in children younger than 4 years old. The National Cancer Institute (NCI) reports that in 2010 just over 24,000 cases of liver cancer were diagnosed and nearly 19,000 people died from liver cancer in the United States.
Viruses
Infection with hepatitis B or C viruses is the most common cause of hepatocellular carcinoma. These viruses are spread by blood exchange or sexual contact and cause irreversible scarring of the liver, also known as cirrhosis, which has a strong correlation with the development of hepatocellular carcinoma. A review in the June 2007 "Gastroenterology" states that people with chronic untreated hepatitis B infection have a likelihood of developing liver cancer that is between five and 15 times higher than the general population. Additionally, this review reports that those chronically infected with hepatitis C virus have a 17-fold increased risk of developing liver cancer over the general population.
Diseases
Hemochromatosis, a disease of excessive iron accumulation, autoimmune hepatitis, Wilson's disease, nonalcoholic fatty liver disease, liver cirrhosis, diabetes and obesity increase the risk of liver cancer. Cirrhosis, which refers to the end stage of chronic liver disease, is the most prominent disease associated with liver cancer. Liver cirrhosis is caused by diseases, alcoholism and hepatitis B and C infection. The review in "Gastroenterology" notes that between 70 and 90 percent of hepatocellular carcinomas occur in patients with cirrhosis. This source also reports that a study on more than 900,000 people in the United States found that liver cancer deaths were five times greater in obese men than in men who had a normal body mass index.
Gender, Race, Genetics
Men are more likely to develop liver cancer than women. The NCI reports that 15,000 men and 6,000 women are diagnosed with liver cancer each year in the United States. Liver cancer is more prevalent in Asian Americans, Pacific Islanders, American Indians, American Blacks and Hispanics than in Caucasians. A review in "Gastroenterology" does state there are likely genetic risk factors for liver cancer, but they have not been identified in studies to date. The review does mention that the risk for liver cancer is higher in people with first-degree relatives who have liver cirrhosis.
Alcohol and Tobacco
A review article in the June 2010 "Orvosi Hetilap" reported that the incidence of liver cancer in patients with alcohol-related cirrhosis is between 3 and 15 percent. While the evidence for alcohol as a risk factor for liver cancer is well established the evidence that tobacco use impacts the incidence of liver cancer is controversial. The review in "Gastroenterology" concludes that the evidence that tobacco use plays a role in the development of liver cancer is weak and may be limited to subsets of a population, such as those that also consume alcohol or are infected with a hepatitis virus.
Chemicals and Toxins
Aflatoxins, which are produced by molds that are found on peanuts, soybeans, corn, rice and wheat, increase the risk of liver cancer. In the United States these foods are tested for the presence of aflatoxins. Chemicals that increase the risk of certain types of liver cancer include vinyl chloride, thorium dioxide and arsenic. The ACS notes that thorium dioxide is no longer in use and the source of arsenic that is of some concern regarding liver cancer incidence is found in contaminated wells. The review in "Gastroenterology" states that the evidence that vinyl chloride causes liver cancer in factory workers is negligible.
Drugs and Hormones
The ACS states that long-term use of anabolic steroids slightly increases the risk of liver cancer. The review in "Gastroenterology" notes that oral contraceptives that contain estrogen and progesterone may play a role in stimulating the growth of liver tumors; however the evidence is inconclusive.
