Carcinoembryonic antigen was originally found in colon cancer and fetal intestinal tissue, hence the name. Elevated serum CEA is seen in cancers of the digestive tract as well as other systems. Continuous monitoring of carcinoembryonic antigen levels can be used to observe the efficacy of tumor treatment and determine prognosis. Serum CEA levels generally decrease when the disease improves and increase when the disease progresses. What is carcinoembryonic antigen? Carcinoembryonic antigen is a glycoprotein produced by colorectal cancer tissues, which can be used as an antigen to elicit immune response from 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 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. (I) Clinical significance CEA was originally found in colon cancer and fetal intestinal tissue, hence the name carcinoembryonic antigen. elevated CEA is commonly found in colorectal cancer, pancreatic cancer, gastric cancer, breast cancer and medullary thyroid cancer. But smoking, pregnancy and cardiovascular diseases, diabetes, non-specific colitis and other diseases, 15% to 53% of patients will also have elevated serum CEA, 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. 97% of healthy adults have serum CEA concentrations below 2.5 μg/L. CEA distribution in primary small bowel cancer Increased CEA in patients with primary colon cancer accounts for 45-80%. In addition to primary colon cancer, the positive rate of pancreatic cancer, bile duct cancer, gastric cancer, esophageal cancer, adenocarcinoma, lung cancer, breast cancer and tumors of the urinary system is also high, generally at 50-70%. CEA is also partially elevated in patients with benign tumors, inflammatory and degenerative diseases, such as colon polyps, ulcerative colitis, pancreatitis and alcoholic cirrhosis, but it is much lower than that of malignant tumors, generally less than 20 μg/L. CEA exceeding 20 μg/L often indicates the presence of gastrointestinal tumors. Therefore, the determination of CEA can be used as a basis for differential diagnosis between benign and malignant tumors. It is an auxiliary diagnostic index of GI tumor, and the reference value is ≤5.9μg/L. (2) Gastric cancer embryonic antigen (CEA) Carcinoembryonic antigen (CEA) is an acidic protein. The CEA content of normal mucosa next to cancer is little or negative. The CEA positivity rate of gastric cancer is 85.58%. Among them, mucinous adenocarcinoma and indolent cell carcinoma (mucinous cell carcinoma) were 100%. The CEA concentration in body fluid and gastric fluid was higher than that in serum because CEA was located in the glycoconjugate envelope around the cell membrane and could be easily released into the surrounding body fluid. The reason for the higher CEA content in the plasma of cancer cells is related to the increased synthesis of CEA in cancer cells and the blocked excretion of CEA. When cancer cells become degenerative and necrotic, the intracellular membrane structure is damaged and ruptured, and CEA can appear in the cytoplasmic matrix. The CEA antigen determinant is glycoprotein, and the infiltration and metastasis of tumor cells are related to the glycosylation of cell membrane glycoprotein. In addition, mucinous cell carcinoma can secrete and release a large amount of proteolytic enzymes, which can destroy the calcium bridges of cancer cells and dissolve the soft tissues around the cancer nests. Therefore, gastric mucinous cell carcinoma is highly invasive and has a high metastasis rate. （The significance of carcinoembryonic antigen is that it can reflect the existence of many kinds of tumors, and can be used to determine the efficacy, development, monitoring and prognosis 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. When the carcinoembryonic antigen (CEA) is high, you can start from the following points: 1. Go to hospital for a comprehensive cancer prevention physical examination. 2.Dynamic monitoring of carcinoembryonic antigen. 3. Have a medical examination by an oncologist and analyze the relevant laboratory results comprehensively. (D) Precautions for carcinoembryonic antigen (CEA) Before the examination: 1. The alcohol content in the blood will directly affect the test results. 2. Fast for 12 hours before blood sampling and take fresh blood for testing. During the test: Relax when drawing blood to avoid vasoconstriction caused by fear, which increases the difficulty of blood collection. After the test: 1. After the blood is drawn, local pressure at the needle hole is required for 3-5 minutes to stop the bleeding. Note: Do not rub to avoid causing subcutaneous hematoma. 2. The duration of pressure should be adequate. The clotting time varies from person to person, and some people need a slightly longer time to clot. So when the skin surface does not seem to bleed immediately stop compression, may not completely stop bleeding, and blood seepage to the subcutaneous cause bruising. Therefore, longer pressure is necessary to stop bleeding completely. If there is a tendency to bleed, the compression time should be extended. 3.After blood sampling, symptoms of dizziness such as dizziness, dizziness and weakness should be immediately laid down, drink a small amount of sugar water, and wait for the symptoms to be relieved before conducting physical examination. 4.If local bruising occurs, wet compress with warm towel after 24 hours can promote absorption.