Liver cancer is the sixth most common cancer and the second highest cause of cancer deaths in the world. While incidences of liver cancer can be found in every region, it is most common in Sub-Saharan Africa and Asia. Though it is primarily caused by hepatitis virus infections, liver cancer has various causes depending on the area in which it is originating. Due to the expensive nature of treatments, prevention and reduction of risk factors should be the primary methods of combating liver cancer.
Prevalence of Liver Cancer
Nearly 85% of cases occur in Southeast Asia, the Pacific, and Sub-Saharan Africa. Over half of these cases occur in China alone and the highest incidence rate is in Mongolia at 78.1 cases per every 100,000 people (Ferlay, et al., 2013). These are the results of infections with hepatitis viruses B (HBV), C (HCV) or a combination of infections with HBV and hepatitis D virus (HDV). Other countries with high levels of liver cancer (more than 20 cases per 100,000 people) include Taiwan, Korea, Laos, Thailand, Vietnam, The Gambia and Guinea (Ferlay, et al., 2013).
Incidence of liver cancer is also much higher in men than in women. Incidence of liver cancer are nearly 2 to 3 fold higher in men in almost every country reporting liver cancer incidences. The difference is especially significant in countries with an intermediate number of cases. However, it is unclear if hormonal or genetic differences may the culprit for these sex differences.
Incidence of liver cancer also increases with age. The highest rates are in people that are 75 years of age and older. In areas with fewer cases, rates are low until the age of 40. However, in countries with a high liver cancer rate, the number of cases among children is very high and increases with age.
Since the greatest risk factor for liver cancer is HBV and HBV is highest in low- and middle- income countries, incidence of liver cancer is also much higher in these countries.
Types of Liver Cancer
The most common form of liver cancer is hepatocellular carcinoma cancer (HCC). HCC originates from liver cells that make up the lining (epithelial cells) of the liver called hepatocytes. Approximately 80% of primary liver cancers are HCCs. Hepatocellular carcinoma cancer is the fifth most common cancer among men and the eighth most common in women,
Cholangiocarcinoma (CC) is a cancer originating from the cells that make up the lining of the bile duct. There are four types of CCs that are broken down into cancer that arises in the liver; intrahepatic and peripheral CC and those that originate in the periphery of the liver; hilar and extrahepatic CC.
The second most common liver cancer called intrahepatic cholangiocarcinoma (ICC) makes up 10-12% of primary liver cancer cases. While the etiology is not completely clear, the primary cause of ICC in high-incidence regions is infection with intestinal parasites such as liver flukes or flatworms.
Other potential causes include disorders that cause chronic inflammation of the bile tract, formation of stones in the bile tract (hepatolithiasis), cysts within the liver, and diseases such as congenital hepatic fibrosis, Caroli’s disease, von Meyenburg complexes and polycystic liver disease.