What are tumor markers? Tumor markers are substances that are secreted by tumor cells or normal cells and shed into body fluids or tissues, or may be produced by the body in response to microorganisms and enter into body fluids or tissues, which we call antigens. The body produces antibodies against these antigens, and the antigen-antibody combination produces immune complexes. Using this principle, in vitro-labeled antibodies are put together with the serum of the test subject, and chemical methods are used to capture the corresponding tumor markers in the serum of the test subject. Most of the tumor markers commonly used in clinical practice are tumor-associated antigens, such as CA125, CA199, CA153, CA72-4, AFP, CEA, HCG, SCC, PSA, NSE, etc. With the rapid development of various immunomarker technologies, the number of tumor indicators detected is increasing. These indicators are of great significance for the auxiliary diagnosis of malignant tumors, evaluation of tumor treatment effects and prognosis. However, tumor markers have their limitations in clinical application. Does an elevated tumor marker necessarily indicate the presence of malignant tumor in the body? In fact, tumor markers are not unique to tumor cells. Tumor markers are influenced by some bioactive factors in the body in the process of production, and are not only produced in malignant tumors and benign tumors when they become cancerous, but are also expressed in varying degrees in benign diseases and even under normal conditions. Glycoconjugate antigen CA199: In gastrointestinal malignancies, 74.9% of pancreatic cancer, 50% of gastric cancer, 60% of colon cancer, and 64.6% of liver cancer will result in a significant increase in CA199. It is elevated in ovarian cancer or ovarian metastatic cancer, lung cancer, and breast cancer. Benign diseases including ovarian teratoma, uterine adenomyosis, acute pancreatitis, cholecystitis, cholangitis, and hepatitis cirrhosis are also seen to be elevated. In physiological conditions, this antigen is found in the pancreas, gallbladder, liver and intestine of embryonic fetuses. Human chorionic gonadotropin β-HCG: physiologically, it starts to rise after pregnancy, peaks at 8-10 weeks of pregnancy and then decreases, maintains a high level until delivery, and decreases to normal 2 weeks after delivery. The rate of beta-HCG multiplies every 2-3 days during early pregnancy, if it does not reach, ectopic pregnancy or embryonic dysplasia should be considered and further examination should be performed. In addition to elevated pregnancy HCG, trophoblastic cell tumors (choriocarcinoma, erosive staphyloma) and ovarian germ cell malignancies (primary choriocarcinoma) associated with pregnancy are significantly elevated. Small bowel cancer, colon cancer, stomach cancer, pancreatic cancer, liver cancer, breast cancer, testicular cancer, and bronchial cancer are elevated to varying degrees. Benign diseases such as endometriosis and ovarian cysts are also sometimes elevated. Alpha-fetoprotein AFP: significantly elevated in primary hepatocellular carcinoma, 77.1% greater than 500 μg/L. Elevated in benign diseases such as viral hepatitis and cirrhosis, AFP gradually returns to normal when hepatocytes are repaired during hepatitis recovery. Ovarian germ cell malignancies such as endodermal sinus tumors and immature teratomas are often elevated. Physiologically, it starts to rise after 3 months of pregnancy and reaches below 400μg/L in July-August, and returns to normal 3 weeks after delivery. Abnormal elevation during pregnancy may indicate the presence of neural tube abnormalities in the fetus. Squamous epithelial antigen SCC: all squamous cancers are elevated in vivo, and squamous cervical cancer can lead to elevation of this marker. Cancer antigen CA153: Breast cancer can lead to significant elevation, and also lung, ovarian, cervical, liver, kidney, colon, and pancreatic cancers. It is also elevated in benign diseases of the gastrointestinal tract, liver, lung, breast, and ovary. Carcinoembryonic antigen CEA: It is a broad-spectrum tumor marker and is elevated in malignant tumors of the digestive system, lung cancer, and breast cancer. It is also elevated in benign diseases such as colitis, rectal polyps, cirrhosis of the liver, hepatitis, and abnormal kidney function. If the patient smokes this indicator may appear abnormal. In summary, elevated tumor markers reflect the possible presence of malignant tumors in the body in most cases, but not 100%. In patients with autoimmune diseases, rheumatoid factor in the body often reacts with the antibodies used to detect tumor markers, which may also cause false positives. Even if there are malignant tumors in the body, tumor markers are not organ specific, different tumors can have the same tumor markers, and the same tumor can have several different tumor markers, so it is impossible to pinpoint the location of the tumor in the body. For example, elevated CA125 does not necessarily indicate ovarian cancer, but can also be seen in patients with lung cancer, gastrointestinal cancer, liver cancer and pancreatic cancer. Tumor markers can also be increased during surgery and radiation/chemotherapy for malignant tumors, when tumor tissue is destroyed or when tumor necrosis occurs. Do tumor markers necessarily increase in malignant tumors or benign tumor malignancy? To date, no tumor markers with 100% sensitivity and 100% specificity have been identified. For example, when the number of tumor cells producing tumor markers in early malignant tumor is small, the cells or cell surface is closed, antibodies in body fluids bind with tumor markers to form immune complexes, and the tumor tissue itself has poor blood circulation and the tumor markers produced by it cannot be released into the peripheral blood. Also, improper collection and storage of blood specimens can lead to negative tumor marker test results. When you get the laboratory report of abnormal tumor markers, do not panic, but seek medical advice and follow the relevant tests. Please remember that tumor markers are an important method to assist in the diagnosis of diseases and tumors, but not the only one. Tumor markers can neither confirm the diagnosis of malignant tumors nor clarify the site of tumors. Tissue biopsy or post-surgical pathological examination is the gold standard to confirm the diagnosis.