After pregnancy, fetal cells remain in a woman's body for years. These cells may be involved in different physiological situations (e.g. wound healing) and diseases (e.g. cancer).The study will evaluate the level of circulating fetal immune cells in patients with breast cancer vs controls with benign breast tumors, and further characterize these fetal cells. Patients participation will be limited to accepting that an additional blood sample is collected on the day of their preop consultation and blood test.

Breast cancer is the most common cancer in the female population. The protective mechanism associated with pregnancy is not fully understood.

During pregnancy fetal cells cross the placental barrier and may remain in the maternal circulation even for up to 30 years after childbirth. This phenomenon is called fetal microchimerism.

The presence of circulating fetal cells would have a protective role against breast cancer. However, their phenotype and role in the anti-tumor response is not explored.

The objective of the study is to identify the sub-population (s) of circulating fetal immune cells that may have an impact on the processes of carcinogenesis in breast cancer, in the context of fetal microchimerism.

Inclusion Criteria:

• women aged 18-50
• having had a male child
• informed and not having objected to participating in the research.

Patients:

- having a diagnosis of breast cancer

Controls:

• operated on for benign breast tumors
• cancer free

Exclusion Criteria:

• autoimmune disease
• immunomodulatory treatment
• history of cancer other than breast cancer
• ongoing hormonal treatment
• women not affiliated to the social security
• under AME (state medical aid)
• under tutorship / curatorship

The study population includes only women who have had a male child, premenopausal, aged 18-50 years, who are operated on for breast cancer or who have just been diagnosed with breast cancer.