Carcino-embryonic antigen is a glycoprotein produced by colorectal cancer tissue that acts as an antigen to elicit an immune response in patients. This antigen, called carcino-embryonic antigen CEA, is widely present in digestive system cancers of endodermal origin, as well as in the digestive tract tissue of normal embryos, and may be present in trace amounts in normal human serum. CEA is a broad-spectrum tumor marker, which can reflect the existence of many kinds of tumors to people. It is a good tumor marker for judging the efficacy, disease development, monitoring and prognosis estimation of colorectal cancer, breast cancer and lung cancer, but its specificity is not strong, sensitivity is not high, and its role in early diagnosis of tumors is not obvious. Introduction of carcinoembryonic antigen CEA Carcinoembryonic antigen was originally found in colon cancer and fetal intestinal tissue, hence the name. Elevated serum CEA is seen not only in GI tract cancer but also in other systems. Continuous monitoring of carcinoembryonic antigen levels can be used to observe the efficacy of tumor treatment and determine prognosis. In general, serum CEA level decreases when the disease improves and increases when the disease progresses. Clinical significance of carcinoembryonic antigen CEA 1. Elevated CEA is commonly found in colorectal cancer, pancreatic cancer, gastric cancer, breast cancer, medullary thyroid cancer and so on. But smoking, pregnancy and cardiovascular diseases, diabetes, non-specific colitis and other diseases, 15%~53% of patients’ serum CEA will also be elevated, so CEA is not a specific marker for malignant tumors, and only has an auxiliary value in diagnosis. In addition, there is a clear relationship between serum CEA level and the stage of colorectal cancer, the more advanced the lesion, the higher the CEA concentration. 2. 97% of healthy adults have serum CEA concentrations below 2.5ng/mI. Increased CEA in patients with primary colon cancer accounts for 45-80%. In addition to primary colon cancer, pancreatic cancer, bile duct cancer, gastric cancer. Esophageal cancer, adenocarcinoma, lung cancer, breast cancer and urological tumors also have a high positive rate, generally at 50-70%. 3, benign tumors, inflammatory and degenerative diseases, such as colon polyps, ulcerative colitis, pancreatitis and alcoholic cirrhosis change patients also have partially elevated CEA, but much lower than malignant tumors, generally less than 20μg/L, CEA more than 20μg/L often suggests the presence of gastrointestinal tumors. Therefore, the determination of CEA can be used as a basis for differential diagnosis between benign and malignant tumors. Detection of carcinoembryonic antigen CEA Carcinoembryonic antigen (CEA), first reported by Gold and Freedman in 1965, is extracted from liver metastases of colon adenocarcinoma and normal fetal gastrointestinal tract. It is considered to be one of the most widely used human tumor-associated antigens. As an immune heterogeneous glycoproteome, CEA has a molecular weight of roughly 200,000 daltons and contains 50-85% carbohydrates . CEA is a member of the immunoglobulin family and exhibits the function of binding intercellular molecules. In addition, substances related to the structure of CEA molecules (e.g. NCA, NCA-2, NFA) have been reported in normal human tissues. The determination of CEA in serum shows potential advantages in the diagnosis and treatment of malignancies, especially colon adenocarcinoma. Post-treatment follow-up can be used to monitor the progression, degeneration and recurrence of the patient’s tumor. A persistent increase in CEA after drug or surgical treatment is often a sign of residual or recurrent tumor, and a decrease in concentration to the normal range is a sign of successful treatment. Elevations are also seen in patients with non-malignant disease or in heavy smokers; therefore, CEA should not be used as a screening indicator for diagnosing cancer or in asymptomatic patients.