Sentinel lymph node (SLN) biopsy is the standard procedure for axillary node staging in breast cancer. Improvements in histopathological analysis and immunohistochemistry have recently increased the rate of detection of lymph nodal micrometastases. The clinical implications and prognostic significance of micrometastases in SLN still remain a controversial issue. Literature review was analyzed by searches of Medline and PubMed data bases. Whereas most studies carried on small groups of patients did not show differences in survival, recently some studies with longer follow-up and with larger populations demonstrated that prognosis of patients with micrometastases is worse compared to that of patients with SLN free of disease. To date, completion axillary dissection remains the standard option when a macro or micrometastasis (0.2-2 mm) in the SLN is found. However, in absence of level-1 evidence guidelines, each case requires discussion in the context of a multi-disciplinary team.