Tumor markers are a class of substances synthesized and released by tumor cells themselves, or produced or elevated by the body in response to tumor cells, mainly including protein, glycans, enzymes and hormonal tumor markers. The five tumor markers may be different in each hospital. The common five tests include the following: 1. alpha-fetoprotein (AFP): AFP disappears from the blood 2 weeks after birth of newborns. When hepatocytes or germinal gland embryonic tissues are malignant, it can lead to different degrees of elevated AFP in blood, such as primary hepatocellular carcinoma, ovarian cancer, teratoma, gastric cancer or pancreatic cancer. In addition, viral hepatitis and cirrhosis can also cause mild elevation of AFP. 2. Carcinoembryonic antigen (CEA): It is a broad-spectrum tumor marker that can be expressed in a variety of tumors, such as pancreatic cancer, rectal cancer, breast cancer, lung cancer and gastric cancer. It is mainly used to assist in the diagnosis of malignant tumors, to judge the prognosis and efficacy, and to assess whether the tumor has recurred. Prostate-specific antigen (PSA): exists in the epithelial cells of the prostate ducts. It is the first choice tumor marker for pancreatic cancer and has a high sensitivity. Continuous examination of CA19-9 is of great value for disease monitoring and efficacy determination. In addition, carcinoembryonic antigen 125, prostate acid phosphatase and calcitonin are also important tumor markers. The same tumor can contain multiple markers, and one marker can also appear in multiple tumors, and the best combination of markers can help in the diagnosis of tumors. Although tumor markers are related to tumors, many benign diseases such as inflammation, polyps and adenomas can also cause elevated tumor markers, which should be distinguished.