Tumor markers have different normal value ranges depending on the type of test used in each hospital. The normal value ranges are different according to different testing methods and should be viewed according to the standard of the hospital. For example, the normal value of carcinoembryonic antigen among tumor markers is ≤15μg/L (ELISA method), and the normal value of serum alpha-fetoprotein content is ≤25μg/L (radioimmunoassay). Tumor markers do not have high specificity and can only be used as the basis for auxiliary diagnosis of cancer, and cannot diagnose whether a patient has cancer according to the tumor marker values. Pathologic examination is the gold standard for definitive diagnosis.