Glycoantigen CA15-3 is a tumor marker that is mainly used as an adjuvant diagnosis for breast cancer. Some of the patients with breast cancer can be significantly elevated, and generally the cost of glycoantigen CA15-3 test is about$100. About 30%-50% of breast cancer patients have significantly elevated CA15-3, however, the positive rate is slightly lower in patients with early stage breast cancer, around 20%-30%. Therefore, in clinical practice, CA15-3 testing is mainly used to observe whether there is recurrence or metastasis after breast cancer treatment. In addition to elevated CA15-3 in breast cancer patients, CA15-3 can sometimes be elevated in patients with metastatic ovarian cancer and colon cancer. In addition, CA15-3 can also be elevated in lung cancer and pregnancy, so it is important to test CA15-3 for the above diseases.