Inclusion Criteria:  Age: 40 ≤75 years old Breast cancer with infiltrating histology Tumor size ≤50 mm (T1 - T2) Clinically and ultrasound node-negative (cN0) breast cancer No distant metastases (M0) No neoadjuvant therapy Negative history of previous infiltrating neoplasm Maximum number of metastatic sentinel lymph nodes: 2 Lymph node macro-metastases > 2mm  Exclusion Criteria:  Pregnancy or breastfeeding in progress Inflammatory breast cancer Breast cancer in situ Synchronous contralateral breast cancer Co-morbidities such as to preclude the possible use of adjuvant therapy Conditions that make it impossible to carry out a regular follow-up Other malignancies within the previous 3 years (except carcinoma in situ of the uterine cervix, basalioma or squamous cell ca or non-melanoma skin ca) Breast cancer with non-infiltrating or inflammatory histotype Tumor size> 50 mm No sentinel lymph nodes identified No positive sentinel lymph nodes (pN0) Positive sentinel lymph node number > 2 Lymph node micro-metastases <= 2