The objective of this clinical trial is to demonstrate the reduction of positive margins in the definitive pathology of patients undergoing breast-conserving surgery with the systematic shaving technique compared to conventional surgery, and the reduction of second interventions for margin enlargement.

Patients with breast cancer who undergo breast-conserving surgery are randomized in the operating room after lumpectomy into 2 groups of 117 patients each: shaving/no-shaving (standard surgery).

Inclusion Criteria:

1. Breast-conserving surgery.
2. Imaging diagnosis as the only breast tumor focus according to mammography, breast ultrasound and/or nuclear magnetic resonance;
3. Pathological diagnosis of carcinoma in situ or infiltrating
4. Oncoplastic without associated flaps;

Exclusion Criteria:

1. Male patients;
2. Patients with a history of ipsilateral breast cancer.
3. Oncoplastic that includes flaps
4. Multifocality or multicentricity;
5. Pregnant or lactating patient;
6. Stage IV patients;
7. Patients eligible for mastectomy;

Randomization will be performed by another investigator outside the operating room after lumpectomy.