Glycoantigen CA50 is a blood test indicator, which is a tumor marker used to assist in the diagnosis of malignant tumors, monitor the development of tumor conditions, and evaluate the effect of anti-tumor therapy. Glycoantigen CA50 is a tumor marker of glycoantigens, which is often found abnormally elevated in gastric cancer, intestinal cancer and other digestive system tumors, and therefore can be used as an auxiliary diagnostic indicator for these diseases, but cannot be used as an indicator for confirming the diagnosis of malignant tumors. Glycoantigen CA50 will generally fluctuate with the development of malignant tumors, so this index can be reviewed regularly to monitor the changes of malignant tumors, but it cannot be used as the only criterion, and should be combined with the imaging or pathological examination of the organs involved in the cancer to make a comprehensive judgment. Moreover, patients with effective anti-tumor treatment will generally show a decrease in the glycoantigen CA50 index, so the glycoantigen CA50 can be tested before and after treatment to evaluate the effect of treatment.