Why do all people with hepatitis B infection need to know about liver cancer? Because the vast majority of liver cancer in China is a consequence of hepatitis B virus infection, which has a high incidence. Hepatitis B virus infection usually occurs in infancy and early childhood, and most of them become chronic carriers; 25% of them develop chronic hepatitis B in adulthood; if antiviral treatment is not used, about 40% of them develop cirrhosis after middle age; 1%-4% of cirrhotic patients who still carry the virus and have active disease will develop liver cancer every year. Why should the diagnosis of liver cancer start with screening test? Liver cancer is a highly malignant tumor. If you seek medical attention only when you have symptoms of liver cancer, most of them are already giant liver cancer, and it is not an indication to replace a liver. The liver cancer that can be cured is mainly “small liver cancer”, which you have to go to it; if it comes to the frivolous liver cancer, the treatment is probably very difficult. What is meant by “small liver cancer”? It means not only because it is small, but because it is a specific stage of liver cancer development. The diameter of small liver cancer should be less than 2 centimeters. At this time, it has an intact envelope and the cancer cells have not yet invaded the blood vessels in the liver. If it is more than 2 cm, it is likely that the cancer cells have already invaded the blood vessels inside the liver or even metastasized outside the liver, and even if it is removed, most of them will still recur. People with “small liver cancer” without symptoms, that is, those who are likely to develop liver cancer, must be checked regularly: ultrasound and methemoglobin every 6 months. It is called “screening test” to start checking for liver cancer when there is no liver cancer yet. Liver cancer develops according to the rule of “multiplication”, initially it is just a small nodule of cancerous cells, maybe less than 1mm (mm), and it may take 2 months to grow to double, while CT diagnosis requires at least 1cm (1cm=10mm), and it takes many months to grow to 2cm. Small hepatocellular carcinoma” must be in the range of “small hepatocellular carcinoma”. At the time of very small nodules of cancer cells, CT cannot detect them yet, and at this time, methemoglobin may have increased, but only 60%-70% of liver cancers will have increased methemoglobin, so it is necessary to check both ultrasound and methemoglobin every 6 months.