Lymphoceles, or seromas, are the most frequent complication following mastectomy and are associated or not with axillary dissection occurring in 10 to 90% of cases. It is defined as the presence of a palpable post operative serous accumulation that is bothersome for the patient and requires a puncture and drainage or even several repeated punctures. The presence of seromas is therefore associated with discomfort and pain. Seromas could also be responsible for increased morbidity due to complications such as infection, suture separating, lymphedema, prolonged of hospital stay, or a delay in initiation of adjunct treatment (e.g. chemotherapy, radiotherapy). Some risk factors have been identified, such as obesity, increased post operative drainage of J1 to J3, and arterial hypertension.

Different measures have demonstrated the benefits of limiting axillary lymphoceles after dissection : placement of a drain, padding and delay in shoulder mobility.

Studies have shown that axillary padding decreases lymphocele development and shortens the length of hospital stay. Some studies based on padding of the mastectomy site also have shown a decrease in post operative seromas; however no study has been done on the usefulness of padding in the mastectomy site alone because they include both padding and a drain or padding of the axillary area.

The padding technique the investigators employ is performed at the donor site in breast reconstruction by latissimus dorsi muscle flap, demonstrating a reduction in the rate of seromas.

In this study, the classic technique will be compared to padding in the mastectomy site with short drainage (48h).

Inclusion Criteria:

• Age ≥ 18 years
• Female gender
• Patients with infiltrating or in situ breast cancer
• Indication of surgical treatment by mastectomy
• Patient providing written informed consent
• Patient with health insurance coverage
• Ability to provide voluntary written informed consent

Exclusion Criteria:

• Informed consent cannot be obtain
• Pregnant or lactating women
• Patients undergoing immediate breast reconstruction
• Patients with cancer untreatable by mastectomy, non curative mastectomy: partial mastectomies, preventive mastectomies (BRCA genetic mutations)
• Patients under legal protection or unable to come to a center
• Patients unable to express voluntary consent
• Patients receiving post operative anticoagulants or platelet antiaggregants
• Patients requiring postoperative anticoagulants
• Bilateral mastectomy