The investigators aim to evaluate the possibility of clinical application of ctDNA detection in peripheral blood of normal people, benign breast disease patients and breast cancer patients, so as to act as the new techniques or indicators of early screening of breast cancer.

Inclusion Criteria:

• Written informed consent must be obtained and documented according to the local regulatory requirements prior to beginning specific protocol procedures.
• Age of at least 18 and at most 70 years.
• Normal people who works as the volunteers.
• Benign breast disease patients should be diagnosed with confirmed pathology after surgery.
• Breast cancer patients should be diagnosed with confirmed pathology after surgery, and with no clinical evidence of local recurrence or distant metastases. Complete staging work-up within 3 months prior to registration, which should be earlier than TNM IIA stage.
• Adequate organ function including normal red and white blood count, platelets, serum creatinine, bilirubin, and transaminases within normal range of the institution.

Exclusion Criteria:

• Known hypersensitivity reaction to the investigational compounds or incorporated substances.
• Local recurrence and/or metastasis of breast cancer.
• Pregnant or lactating patients. Patients of childbearing potential must have a negative pregnancy test (urine or serum) within 14 days prior to registration.
• Prior or concomitant secondary malignancy (except non-melanomatous skin cancer or carcinoma in situ of the uterine cervix).
• Other serious illness or medical condition that may interfere with the understanding and giving of informed consent and the conduct of the study.
• Concurrent treatment with other experimental drugs or any other anti-cancer therapy.
• Males.

Three groups: normal people, benign breast disease patients and breast cancer patients in early stage.