Sentinel Node Vs Observation After Axillary Ultra-souND

The hypothesis of this trial are that: * avoiding axillary surgery does not worsen the outcome of patients with small breast cancer the absence of the pathological information on the risk of recurrence given by nodal status is not worsening outcome of these patients * pre-operative imaging of the axilla can identify patients with clinically relevant nodal burden. The aims of this prospective randomized study are: * to verify whether, in presence of a negative preoperative axillary assessment, SLN can be spared * to verify whether, in presence of a negative preoperative axillary assessment, the decision on adjuvant medical treatment can be taken according only to the biology of the tumour without the prognostic information achieved by SLNB on the nodal status * to verify whether, in presence of a negative preoperative axillary assessment, the patients\' quality of life can be improved by a less invasive surgical procedure.