The liver is the largest solid organ in the human body, weighing approximately 1200-1500 grams and located in the upper right abdomen. The liver has essential and complex functions, closely related to digestion, metabolism, storage, detoxification, blood coagulation, and other processes. The gallbladder is located below the right lobe of the liver, and the liver continuously secretes bile through the biliary system into the small intestine to maintain the digestion of food. The digestion and absorption of fatty foods depend on the action of bile. Malignant tumors that occur within the liver are referred to as primary liver cancer or hepatocellular carcinoma, commonly known as liver cancer. It is one of the most common malignant tumors worldwide. Liver cancer that occurs due to the metastasis of cancer from other parts of the body is called liver metastatic cancer.
Currently, the main three etiological factors are hepatitis B virus infection, food contamination by aflatoxin, and water pollution.
Persistent infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) can lead to chronic hepatitis, liver cirrhosis, and in some cases, hepatocellular carcinoma.
In China, approximately 80% to 90% of hepatocellular carcinoma patients are carriers of hepatitis B surface antigen (HBsAg positive), while the HBsAg positive rate in the general population is about 8% to 15%. Immunohistochemical examination shows that hepatocellular carcinoma has a distinct background of hepatitis B virus infection. Molecular tumor studies have confirmed that hepatocellular carcinoma patients have integration of hepatitis B virus DNA (HBV-DNA). The proportion of HBV-DNA integration in hepatocellular carcinoma patients in China is about 68.2%.
HBsAg-positive hepatocellular carcinoma patients have a positive rate of HBV-DNA greater than 90%. Studies have shown that HBV-DNA integration can activate some oncogenes and cause mutations in some tumor suppressor genes. The risk of hepatocellular carcinoma in HBsAg-positive individuals is more than 100 times higher than in negative individuals. Due to the variation of hepatitis B virus (HBV) gene, hepatitis markers are often absent in the serum; only by using PCR (polymerase chain reaction) technology to directly detect HBV-DNA can the diagnosis of HBV infection be more accurate. It has been proven by international research that hepatitis viruses can cause hepatocellular carcinoma. European scholars believe that vaccination of infants in high-risk areas with hepatitis B vaccine can reduce the number of hepatocellular carcinoma patients by 80%.
In Japan and southern Europe, hepatitis C virus (HCV) infection is more closely related to liver cancer. Among patients with viral hepatitis in China, the proportion of HCV infection is relatively low, ranging from 11% to 23%. Hepatitis D virus (HDV)induced liver cancer is less reported, but in former Soviet liver cancer patients, the positive rate of HDV antibody was as high as 81%. It has been found that hepatitis patients need at least 3 to 5 years to develop liver cirrhosis, and it takes about 20 to 50 years for chronic hepatitis to develop into primary liver cancer. It takes about 40 to 50 years for hepatitis B virus (HBV) infection to develop into liver cancer, and about 28 years for hepatitis C virus (HCV) infection to develop into liver cancer.
Secondly, intake of food containing aflatoxin.
In warm and humid areas, foods such as corn and peanuts are prone to mold growth, and the fungi produce aflatoxin and other carcinogens that can cause liver cancer. Chinese people are easily exposed to mold and its metabolites in their daily lives. Since the 1960s, experimental studies have confirmed that more than 10 types of mold toxins can induce tumors in various organs of animals. Aflatoxin has a strong carcinogenic effect, its carcinogenicity is 900 times stronger than butylate and 75 times stronger than dimethylnitrosamine.
In China, researchers fed animals with food containing aflatoxin from liver cancer high-incidence areas, and only 6 months later, the incidence of liver cancer reached 80%. The induced liver cancer was mostly hepatocellular carcinoma. In 1969, the International Agency for Research on Cancer confirmed that aflatoxin is carcinogenic to humans. From 1987 to 1989, researchers from the Shanghai Medical University and the Fusui County Liver Cancer Research Institute in Guangxi Province conducted a study on the relationship between aflatoxin and liver cancer. The results showed that the intake of aflatoxin B1 was positively correlated with the mortality rate of liver cancer,即 the greater the intake, the higher the mortality rate. The main source of aflatoxin is contaminated corn and peanut oil. When foods containing aflatoxin are ingested, they are absorbed in the liver, causing hepatocellular degeneration and necrosis, eventually leading to liver cancer.
Thirdly, drinking water factors: Pollution by certain chemical carcinogens and a specific type of algae.
Water pollution is also related to the occurrence of liver cancer. The mortality rate of liver cancer is directly proportional to the degree of water pollution. Data from high-incidence areas of liver cancer suggests that the mortality rate among residents who drink water from ditches and ponds is 60 to 100 per 100,000 people, while those who drink well water or deep well water have a mortality rate of less than 20 per 100,000 people. With the advancement of water analysis technology, more than 100 carcinogenic, tumor-promoting, and mutagenic substances have been detected in polluted water. In 1991, a type of blue-green algae was discovered in Chinese ditch water that produces algal toxins, which have been proven to be a strong tumor promoter.
- Alcoholism: Regular alcohol consumption can damage the liver’s detoxification function, leading to alcoholic liver disease, which further develops into liver cancer. Therefore, alcoholism is an accessory factor in the occurrence of liver cancer.
- Selenium deficiency: Selenium is a cancer-preventing element, and its deficiency in the body promotes the formation of liver cancer.
- Familial inheritance: Liver cancer has a significant familial aggregation. In families with a blood relationship, the number of liver cancer patients is much higher than that of non-blood relatives, and patients with close relatives are more common than those with distant relatives.
- Combined action of environmental and genetic factors: Research shows that the occurrence of liver cancer is the result of the combined action of environmental factors and genetic factors.
In summary, the occurrence of liver cancer is not due to a single cause but to the combined action of multiple factors. To prevent liver cancer, we should pay attention to our lifestyle, diet, and family genetic factors. In daily life, maintain good habits and diet, supplement selenium and other nutrients appropriately, and undergo regular check-ups to reduce the risk of liver cancer.