Breast cancer is the most common malignant neoplasm in women. Cancer metastases are the main cause of death in these patients. The most common way of metastases spreading is through the lymphatic system. Two main directions of spread of metastases are the lymph nodes of the internal mammary chain and the axilla. It is extremely important to determine which lymph nodes are affected by metastases in order to define the stage of the disease and the correct therapy. For more than 100 years, axillary lymph node dissection (ALND) has been the main method of determining metastatic spread of disease to the lymph nodes and regional disease control. Although it was an effective method, ALND was associated with numerous complications such as lymphedema, reduced mobility of the shoulder zone, pain and paresthesia’s. Then, in 1990, sentinel lymph node biopsy (SLNB) was introduced as a method that could be used to perform regional staging of tumors while avoiding axillary lymph node dissection and its side effects. SLNB assumes that lymph, which carries metastatic cells, is drained in a certain order. If the sentinel node (which is defined as the first node on the cancer path) is not affected, there is little possibility that the metastases have affected the other nodes in the series. Numerous studies have proven that SLNB is as effective as ALND in terms of regional disease control, but with much fewer side effects.