AFP is the abbreviation of AlphaFetalProtein, which means alpha fetal protein, abbreviated as alpha fetoprotein or fetal nail globule. It is a special glycoprotein synthesized by hepatocytes during the embryonic period, which can promote rapid proliferation of fetal liver tissue, so the content in fetal blood is high, but it basically disappears about 1-4 weeks after birth, and the content in adult blood is very little. More than 400ug/L is considered as high concentration positive. Liver cancer, one of the most common malignant tumors in China, is known as the king of cancers! As most of the patients are in the middle and late stages when they are clinically detected, under the ravages of cancer, they have gone through a lot of hardships and suffer a lot of human torments, and eventually they cannot avoid death. In order to effectively treat liver cancer, early detection, early diagnosis and early treatment (often called “three early stages”) are the key, and early diagnosis is the most important part. However, cancer cells are like hidden killers in the sea of people, which are hard to be recognized. In recent decades, scientists have done a lot of researches to solve the case qualitatively through the “traces” left by the “killers” by the needle-in-a-haystack type of laboratory tests. Clinically, such traces are called “cancer markers”, and AFP is the most specific marker for liver cancer. Because the liver itself is a blood pool, as long as there is a 0.1-0.2 cm cancer mass, AFP may be found to be elevated in the blood, which is still difficult to be detected by ultrasound, CT, MRI and other imaging examinations (usually the cancer mass should be around 1.0 cm to be diagnosed by imaging). Therefore, a positive laboratory test for liver cancer can sometimes precede a positive imaging test by several months to about a year, which can win patients valuable and perhaps destiny-determining treatment time! By detecting AFP, medical professionals can screen for liver cancer in the population or diagnose it clinically, and take surgery or corresponding treatment, which has enabled many liver cancer patients to prolong their lives or even eventually overcome liver cancer. In primary hepatocellular carcinoma, 70-90% of patients are positive for AFP. Usually the serum concentration of AFP correlates with the size of the mass and the degree of differentiation of the tumor cells. Normal hepatocytes do not produce AFP, while cancerous hepatocytes regain the ability to synthesize AFP, and the concentration of AFP can increase progressively with the crazy multiplication of cancer cells. Therefore, patients with hepatocellular carcinoma show persistent and high concentration of AFP positive with the course of the disease, usually above 400ug/L. It has been suggested that if AFP is greater than 200ug/L for more than 8 weeks; or greater than 400ug/L for more than 4 weeks, the clinical diagnosis of primary liver cancer can be made after excluding the possibility of pregnancy and genital embryonal tumor. However, does elevated AFP necessarily mean liver cancer? That is not necessarily! This is because there are also the following factors: 1. False positive: No test can be 100% correct, and AFP measurement can also have the problem of false positive, i.e. no liver cancer has occurred but AFP is positive. In this case, AFP should be observed dynamically and combined with imaging and other laboratory tests to exclude it. 2.Benign liver disease: acute hepatitis, chronic active hepatitis, cirrhosis and other liver diseases, because the virus replicates and proliferates in the liver cells, the liver cells are in the process of damage, repair and regeneration, AFP will increase, but the concentration is generally not too high, mostly less than 200ug/L, and with the improvement of hepatitis, AFP also decreases, and then gradually return to normal. AFP elevation is transient and positive at low concentrations. This helps to distinguish AFP from hepatocellular carcinoma, which is a persistent, high level of positivity. However, in a small number of patients with benign liver disease, AFP may also be positive in high concentrations, with values greater than 400ug/L and even as high as 6000ug/L, due to persistent and excessive regeneration of hepatocytes and immature differentiation of the regenerated hepatocytes to synthesize large amounts of fetal nail cells. However, if the degree of liver damage is mild (which can be observed by changes in liver enzymes such as ALT and AST), and AFP continues to be positive in high concentration, the occurrence of liver cancer should be highly alerted. 3.Embryonic tumor: Because AFP has embryonic biological characteristics, it will increase during pregnancy and when malignant embryonic tumor of reproductive system (such as testicular teratoma, ovarian cancer, etc.), but then there should be occupying lesions of genitalia without the basis of liver cancer for differentiation. 4.Other: congenital biliary atresia, abnormal tyrosine metabolism, some secondary hepatocellular carcinoma, some benign tumors of liver and other diseases are also reported to have different degrees of AFP elevation. 5.The rise and fall of AFP can be used as an indicator to judge the prognosis of liver cancer or to observe the effect of surgery and various anti-cancer treatments: after the diagnosis of liver cancer and the adoption of surgical resection or various treatments, a significant decrease of AFP indicates that the treatment is effective; if it increases again after the decrease, it indicates that liver cancer has signs of recurrence and metastasis. In conclusion, AFP is a good indicator for monitoring liver cancer, especially for early diagnosis of small liver cancer, but clinical practice is complex and varied. It is inappropriate to make a diagnosis of hepatocellular carcinoma on the basis of AFP elevation alone, even if it is persistent and high concentration positive, and must be combined with medical history, symptoms, and various laboratory and imaging data to make a correct diagnosis. Then, what should be done once AFP is elevated? The correct attitude should be: attach great importance to it, no need to panic. All AFP-positive patients, especially those with persistent high levels of positive hepatitis B or C, should be considered as high-risk groups for monitoring and should be closely and regularly followed up under the guidance of a doctor.