Axillary lymph node status is a major prognostic factor in early-stage breast cancer. It provides information important for the following surgical procedures. Since imaging techniques have limited sensitivity for the detection of metastasis in axillary lymph nodes, the axilla must be surgically explored. The histology of all resected nodes at the time of axillary lymph node dissection (ALND) has traditionally been regarded as the most accurate method for assessing metastatic spread to regional lymph nodes. However, ALND is often connected to lifequality - reducing side - effects such as lymphedema, dysesthesia, shoulder dysfunction, and other short-term and long-term complications. Sentinel lymph node biopsy (SLNB), introduced in the 1990s, was a milestone that permitted avoidance of axillary dissection if the sentinel node was disease-free. SLNB is less invasive and it has been verified that there is decreased morbidity and less negative side-effects when compared to axillary lymph node dissection (ALND). SLNB relies on the notion that tumor drains in an orderly manner through the lymphatic system. The sentinel lymph node (SLN) should, therefore, be first affected, and a tumor-negative SLN makes it highly unlikely for the other lymph nodes to be affected. SLNB has been established as the gold standard for regional axillary staging. Its use in breast cancer has been evaluated in several randomized controlled trials and validated in multiple prospective studies. However, even today, there are some unresolved questions concerning SLNB and ALND that are still being debated.