The glycoantigen CA15-3 is secreted by epithelial cells with endocrine function, such as breast, lung, gastrointestinal tract, uterus, etc. CA15-3 can also be detected in the excreta of normal people. therefore, glycoantigen CA15-3 as a tumor marker may be elevated in breast cancer, lung cancer, ovarian cancer, gastrointestinal tract tumors, but it is more obvious in breast cancer. The clinical significance of glycoantigen CA15-3 is as follows: 1. Patients with breast cancer may have significantly elevated CA15-3, so it can be used to assist in the diagnosis of breast cancer. 2. It can be used as an indicator for the observation of postoperative efficacy and prognosis of breast cancer, and is of great value in the diagnosis of recurrence and metastasis. 3. Other malignant tumors also have a certain positive rate, such as lung cancer, colon cancer, ovarian cancer, uterine cancer, etc. 4, Mild elevation is also found in normal people.