(1) Early detection and screening of tumors: The diagnostic agent staging of most tumors is the result of comprehensive judgment based on laboratory tests, radiological diagnosis and clinical symptoms, and tumor markers are important auxiliary tools for tumor diagnosis. In early asymptomatic patients, tumor markers are often important and even the only clue to detect tumor. There are not many indicators with census significance. AFP and prostate-specific antigen (PSA) are two indicators that are widely used in census worldwide because they have high organ specificity. For example, AFP suggests liver cancer and PSA suggests prostate cancer. (2) Prognostic judgment of tumors: It helps to determine the prognosis. For example, estrogen receptor and progesterone receptor in breast cancer, if both are negative, even if the glycoconjugate chain antigen CA15-3 is not too high, the prognosis is poor, the chance of recurrence is high and the treatment is not effective. Abnormal epithelial growth factor receptor (EGFR) and oncogene C-erb-2 encoding protein suggest poor prognosis. (3) Efficacy monitoring of tumor treatment: the degree of decline of markers can reflect the treatment effect to a certain extent. (4) Indicators of tumor recurrence: Tumor markers should be measured every 2-3 months during the review phase of malignant tumors and continuously for at least 2 years. After treatment, if the tumor markers continue to rise, a comprehensive examination should be conducted to detect tumor recurrence and metastasis as early as possible. Supplementary: For lung cancer, common tumor markers include SCC (indicating squamous cell carcinoma), NSE (indicating small cell carcinoma), CYFR21-1 (indicating non-small cell lung cancer), and CEA (indicating adenocarcinoma). Sometimes for lung cancers where pathology is not available, we cannot specify the type of pathology and will refer to tumor markers when choosing chemotherapy regimens. The detection of EGFR mutation in non-small cell lung cancer is significant, not only to guide the targeted drug is treatment, but also to suggest a better prognosis and survival.