I. Sources 1. Metabolic products of tumor cells, such as: glycolysis products, tissue peptide antigens, nucleic acid breakdown products. 2.Disordered differentiation cell gene products, such as: ectopic ACTH fragment, methemoglobin, carcinoembryonic antigen, fetal isoenzyme. 3.Materials released into the blood circulation by necrotic disintegration of tumor cells, mainly certain cytoskeletal protein components, such as cytokeratin fragment antigen 21-1 (Cyfra21-1), polyamines. 4. Cellular reactive products of tumor host cells, such as: VCA-IgA, EA-IgA. Common tumor markers in physical examination II. Common physical examination items can be classified as follows: 1. Serum carcinoembryonic antigen (CEA): normal value is less than or equal to 3.45 micrograms/liter. Initially, CEA was found to be elevated in colon cancer patients, and later it was found that 30% of patients with stomach, urethra, ovarian, lung, pancreatic, breast, medullary thyroid, bladder and cervical cancers had elevated blood CEA. 2.AFP: AFP is the earliest discovered tumor marker and is a common test for diagnosing primary liver cancer. About 87% of patients with primary liver cancer have AFP up to 20 μg/L or more. 3.Prostate specific antigen (PSA): the normal value is less than 4 micrograms/liter, the positive rate in prostate cancer is as high as 30% to 86%, and its elevated level is closely related to the tumor. 4.Chorionic gonadotropin (HCG): normal blood concentration is less than 5 micrograms/liter, but HCG can be elevated in patients with chorionic epithelial carcinoma, embryonal malignant teratoma of testis and ovary, and the amount of HCG in blood and urine is associated with prognosis. Uses 1.Early detection of tumor; 2.Census and screening of tumor; 3.Diagnosis, differential diagnosis and staging of tumor; 4.Monitoring the efficacy of surgery, chemotherapy and radiotherapy for tumor patients; 5.Indicator of tumor recurrence; 6.Prognosis judgment of tumor; 7.Search for the primary foci of metastatic tumor of unknown origin. The sensitivity or specificity of single marker is often low and cannot meet the clinical requirements. In theory and practice, it is advocated to measure multiple markers at the same time to improve the sensitivity and specificity. 2. Tumor markers are not the only basis for tumor diagnosis, but need to be combined with clinical symptoms, imaging examination and other means for comprehensive consideration in clinical practice. The diagnosis of tumor must be based on histopathology or cytopathology. 3. Due to the individual differences of patients and their specific clinical conditions, the analysis of tumor markers should be combined with clinical conditions and compared from multiple perspectives in order to reach objective and realistic conclusions. 4.Some tumor markers can also be abnormally elevated in certain physiological conditions or in some benign diseases, which need to be distinguished.