Sentinel lymph node biopsy was shown to be an accurate procedure in the study of axillary lymph nodes; it allowed a marked decrease in surgery-related morbidity of breast cancer and axillary dissection could be avoided. Other parameters as molecular markers, nuclear grading, patient age, tumor size, are not able to predict the axillary lymph node status and consequent local therapeutic approach similar to those provided by sentinel lymph node biopsy. The extent of sentinel lymph node metastatic involvement, the extracapsular spread, the size of primary tumor and peritumoral lymphatic/vascular infiltration are the four characteristics shown to be significant, if considered in association and not separately as predictors of the extent of axillary involvement in presence of a positive sentinel lymph node. However, so far, specific studies did not confirm concordant and reproducible results. Therefore, apart from controlled studies, axillary dissection is always required in presence of a metastatic sentinel lymph node.