CEA is carcinoembryonic antigen. CEA is a test to check the concentration of carcinoembryonic antigen in the blood and is mainly used as an aid in the diagnosis of malignant tumors. Carcinoembryonic antigen is a glycoprotein embryonic antigen found in fetal or colon cancer tissues. In many patients with malignant tumors, such as gastrointestinal cancer, lung cancer, breast cancer, etc., cancer cells can release carcinoembryonic antigen into the blood, resulting in elevated concentrations in the blood, and testing for carcinoembryonic antigen concentration can provide clues to the presence of cancer cells in the patient’s body. However, it is important to note that carcinoembryonic antigen testing cannot be used as a basis for cancer diagnosis alone, but must be considered together with other tests to make a diagnosis. In addition, detection of carcinoembryonic antigen concentration in the blood of cancer patients can also monitor the effect of anti-tumor treatment and predict possible tumor recurrence. If a cancer patient has a high concentration of carcinoembryonic antigen in blood, the concentration will slowly decrease to normal after surgery or chemotherapy if the effect is significant, and similarly, if the cancer recurs, the concentration of carcinoembryonic antigen may gradually increase again.