Breast cancer patients undergoing a mastectomy or breast-conserving procedure are candidates for axillary sentinel lymph node dissection (SNLD) if there is no palpable or clinical evidence of axillary lymph node involvement. The finding of breast cancer metastases in axillary lymph nodes changes the staging of the disease, predicts the rate of recurrence and survival, and results in adjuvant treatment with chemotherapy, hormone therapy, or radiation therapy. The standard axillary lymph node dissection of level I and II nodes has significant morbidity, of which lifelong lymphedema is the most feared by patients. Using a combination of radionuclide and dye injections, the correlation of SLND and standard axillary lymph node dissection (ALND) in finding positive lymph nodes is quite high (95 percent) in the hands of an experienced surgeon. However, sentinel lymph nodes are often only identified in 90 to 95 percent of the dissections. Additionally, a false-negative finding occurs in 3 to 10 percent of the patients having SLND—that is to say, the sentinel nodes are negative, but higher nodes are found to be positive. The advantages of SLND are the fewer complications versus ALND and the ability to identify sentinel lymph nodes that are not in the traditional level I or II areas. The identification of sentinel lymph nodes focuses the histiopathologic examination, which may include immunohistochemical staining as well as the traditional hematoxylin and eosin (H&E). The importance of a micrometastases (<2 mm) is under study; however, the total number of nodes involved with metastases may influence the adjuvant therapy that is offered. Contraindications to SLND include locally advanced primary cancers (>5-cm size); suspicious, palpable axillary lymphadenopathy; multicentric primary breast cancers; prior axillary surgery; and regional breast operations (e.g., breast reduction) that alter normal lymphatic flow.