We all know that carcinoembryonic antigen is a tumor indicator, how to interpret its elevation? In the process of human development, many proteins originally only exist in the placental period, which should gradually stop synthesizing and secreting with the birth of fetus, but due to the influence of some factors, especially in the tumor state, some genes that are “turned off” in the body will be activated, and the phenomenon of reversion will occur, and these embryonic and fetal proteins will be reopened and secreted again. These proteins are produced and secreted again during the embryonic and fetal stages. One of these proteins is carcinoembryonic antigen (CEA), a component of normal embryonic tissue that disappears after birth or is only present in very small amounts. When cells become cancerous, the expression of these antigens can increase significantly. CEA is called carcinoembryonic antigen because it was first found in colon cancer and fetal intestinal tissue. Elevated CEA is commonly found in colorectal cancer, gastric cancer, pancreatic cancer, small cell lung cancer, breast cancer, and medullary thyroid cancer. However, serum CEA may also be elevated in patients with smoking, pregnancy and cardiovascular diseases, diabetes, renal insufficiency, non-specific colitis, colon polyps, chronic liver disease, biliary tract inflammation, pancreatitis, emphysema, etc. Therefore, CEA is not a specific marker for malignant tumors and has only an auxiliary value in diagnosis. It is not sensitive to the early diagnosis of tumor, and CEA may not be elevated in many patients with malignant tumor, but usually the CEA level is mildly elevated in benign diseases, usually not more than 10ng/mL. If the CEA concentration is higher than 10ng/mL, it should be combined with clinical symptoms and physical examination to further determine whether there is a possibility of malignant disease. If there is no abnormality, CEA value changes can be observed in regular follow-up. In conclusion, CEA is a broad-spectrum tumor marker, which has some overlap in benign and malignant diseases, and is neither sensitive nor specific for tumor determination. At present, CEA is mainly used in clinical practice for: 1. screening of malignant tumors, observation of the efficacy of malignant tumors and prognosis judgment. 2. 2. It is mainly used to monitor the recurrence of tumor and the effect of treatment after surgery.