Axillary lymph node excision of level I and II with at least 10 lymph nodes is the operative gold standard for invasive breast cancer. Axillary lymph node excision is a diagnostic procedure for histopathologic tumor classification, for assessment of prognosis, local tumor control and adjuvant therapy decision. The sentinel node biopsy is a minimal-invasive procedure to determine the axillary lymph node status by excision of one or more sentinel nodes. This procedure is being increasingly implemented in breast cancer surgery. The classical axillary lymph node excision can be replaced by sentinel node biopsy if sentinel nodes are free of invasion in the intraoperative as well as in the final histopathological report. Sentinel node biopsy can become an operative routine procedure only in a quality-controlled environment.