This study screened and identified effective methylation markers in breast cancer, established a detection system for early screening and early diagnosis, and provided a research basis for the embryonic form of non-invasive breast cancer early screening products in later incubation. Then, the plasma ctDNA polygene methylation test was performed for early and middle stage breast cancer patients who were to receive radical surgery for initial treatment, and the predictive effect of postoperative plasma ctDNA methylation status on postoperative prognosis of breast cancer was discussed. In addition, the application value of dynamic monitoring of ctDNA methylation in plasma for postoperative recurrence risk monitoring was explored through regular postoperative follow-up of stage I-III breast cancer patients undergoing radical surgery.

1. This study will be divided into two stages. The first stage will complete the screening, identification, model construction and target verification of polygene methylation markers in the blood of breast cancer patients. The second stage will explore its application in monitoring prognosis and recurrence after radical mastectomy.
2. The first stage (inclusion detection period) : By detecting the DNA methylation characteristics of breast cancer (including tissue and plasma) and non-breast cancer samples (breast tissue/plasma of healthy people, and plasma samples of patients with benign breast lesions), screening, identification and verification of plasma ctDNA polygene methylation markers that can distinguish the differences between breast cancer and non-breast cancer samples are carried out.
3. The second stage (postoperative monitoring and evaluation) : The enrolled group was the initially treated patients who planned to undergo radical mastectomy. Plasma methylation markers were detected before surgery at baseline, and dynamic monitoring of plasma ctDNA polygene methylation detection, related tumor markers and imaging examinations were performed 3 weeks after surgery (or before the start of chemotherapy) and regular follow-up review (once every 3 months for 2 years). To explore the clinical application value of ctDNA methylation status in postoperative breast cancer surgery and follow-up monitoring.

The first stage Inclusion Criteria：

Women between the ages of 18 and 80 who are not pregnant or lactating; Meet any of the following categories:

1. Breast cancer Newly diagnosed breast cancer patients [according to breast cancer TNM staging]; The patient was not accepted prior to blood collection Any breast cancer antitumor related treatment, including surgery, transplantation, radiation, chemotherapy, etc.
2. precancerous lesions Dysplasia, carcinoma in situ, atypical hyperplasia, etc., no previous history of malignant tumor.
3. Benign lesions These include fibroadenoma of the breast, intraductal papilloma of the breast, cystic hyperplasia of the breast, lobulated tumors of the breast, Plasma cell mastitis.
4. Healthy people No abnormal breast, no history of malignancy within 5 years; Age 50 years or above.

Exclusion Criteria:

1. previous breast cancer;
2. A history of other cancers;
3. Patients who have received major surgical treatment such as blood transfusion or transplantation within 3 months
4. Participate in other interventional clinical researchers, pregnant or lactating women, or patients suffering from autoimmune diseases, genetic diseases, mental disorders, etc., within 3 months.
5. Patients with other diseases deemed unsuitable for inclusion by the researcher;

The second stage Inclusion Criteria：

1. Patients with definite pathological diagnosis of breast cancer who were to receive radical surgery after preoperative evaluation for initial treatment
2. Women aged between 18 and 80 who are not pregnant or lactating;
3. The radical surgery to be received includes mastectomy radical surgery, simple excision + sentinel lymph node biopsy and modified radical surgery, and on this basis, mastectomy plastic surgery, stage I reconstruction and other operations that have the same radical treatment effect and do not affect the entire standardized treatment of patients
4. Enrolled patients were newly treated breast cancer patients without prior malignant tumor history and treatment history

Exclusion Criteria:

1. Stage IV breast cancer patients, or ECOG score > 2.
2. A history of malignant tumor or other hereditary diseases;
3. Have received organ transplantation, stem cell transplantation, bone marrow transplantation or received blood transfusion within the past month;

1000-1050 samples were used for molecular screening model construction and 100 breast cancer patients awaiting radical surgery were used for 2-year follow-up after treatment