Sentinel lymph node biopsy might replace complete axillary dissection for staging of the axilla in clinically N0 breast cancer patients and represent a significant advantage as a minimally invasive procedure, considering that about 70% of patients are found to be free from metastatic disease, yet axillary node dissection can lead to significant morbidity. In our Institute, Radioguided Occult Lesion Localization is the standard method to locate non-palpable breast lesions and the gamma probes is very effective in assisting intra-operative localization and removal, as in sentinel node biopsy. The rapid spread of sentinel lymph node biopsy has led to its use in clinical settings previously considered contraindications to sentinel lymph node biopsy. In this contest, we evaluated in a large group of patients possible factors affecting sentinel node detection and the reliability of sentinel lymph node biopsy carried out after large excisional breast biopsy. Our data confirm that a previous breast surgery does not prohibit efficient sentinel lymph node localization and sentinel lymph node biopsy can correctly stage the axialla in these patients.