Sentinel lymph node biopsies (SLNB) are changing the management of patients with breast cancer. Although SLNB result in less morbidity than level I and II dissections, equivalence of long‐term survival results should not be assumed. Micrometastases as defined by American Joint Committee on Cancer (AJCC) staging criteria appear to be an adverse prognostic factor and are now being used in practice to identify patients with invasive cancer who should receive adjuvant therapy. Based on present data, isolated cancer cells or small clusters should be disregarded when making recommendations about adjuvant systemic therapy.