AFP is an abbreviation for alpha-fetoprotein, a protein secreted by the human embryo or yolk sac, which is found mainly in fetal blood and at very low levels in normal adult blood. It is mainly found in the blood of fetuses and is very low in the blood of normal adults. Clinically, detection of fetoprotein in blood is mainly used to assist in the diagnosis of hepatocellular carcinoma because liver cancer cells can secrete large amounts of this protein into the blood, resulting in elevated blood fetoprotein concentrations. Currently, testing blood methemoglobin concentration, combined with liver ultrasound examination, is the main means of clinical screening for liver cancer. However, it should be noted that besides liver cancer, various acute and chronic hepatitis, liver cirrhosis, and gonadal tumors such as ovarian cancer and testicular cancer can also lead to some degree of elevated blood AFP levels. Therefore, fetoprotein test alone cannot be used as a basis for diagnosis of liver cancer, and must be combined with other tests to confirm the diagnosis.