Axillary lymph node dissection has been an integral component in the surgical management of invasive breast cancer for many years. For most of this century, axillary dissection was thought to be both prognostic and therapeutic and was considered an important component of surgical cure. En bloc resection of the axillary lymph nodes was the standard of surgical therapy . In the 1970s, Fisher suggested that breast cancer is a systemic disease at presentation, implying that small tumors may represent an early manifestation of a disease process that is already metastatic . Therefore, nodal involvement becomes not an orderly contiguous extension as described by Halsted but rather a marker of distant disease. Fisher proposed that regional lymph node metastases are of biologic importance and an indicator of a poor tumor-host relationship. Axillary nodal metastasis remains the best and most important prognostic marker and remains the single strongest predictor of survival in women with breast cancer [3,4]. As a result of this, the National Institute of Health (NIH) Consensus Conference of 1991 recommended a Berg Level I and II axillary node dissection for patients with early-stage invasive breast cancer . This will provide accurate information regarding the axillary nodal status and is associated with a low rate of axillary recurrence.
Although axillary node dissection has a low false-negative rate, it does result in significant morbidity. Permanent lymphedema has been reported in 1530% of patients undergoing axillary dissection and the frequency, and severity of this complication increases with the extent of axillary surgery and the addition of radiation therapy [6-8]. Other complications such as wound infection, seroma, arm weakness, decreased shoulder range of motion, and neurologic changes can occur. These sequelae are a major source of emotional distress and functional impairment for women with breast cancer and they significantly increase the monetary cost of the procedure [6,11]. Unfortunately, there is no accurate alternative to histologic assessment of the axillary nodes. Clinical evaluation has been associated with a high false-negative rate ranging from 29-38% and a false-positive rate of 10-50%. Radiological evaluation using mammography, ultrasound, computed tomography (CT) scan, magnetic resonance imaging (MRI), and nuclear medicine evaluation using lymphoscintigraphy, positron emission tomography (PET), and radiolabeled monoclonal antibody scanning may detect axillary nodal metastases, but these techniques lack the sensitivity and specificity that are needed for clinical decision-making [12-16].
Over the last few years the need for axillary dissection for women with invasive breast cancer has been questioned. This is in part due to the increasing use of mammography and the detection of smaller tumors, which has led to a decreased incidence of nodal metastases in this subset of women. Adjuvant therapeutic decisions once based on the nodal status are no longer limited to patients with node-positive breast cancer and are now often dependent on the characteristics of the primary tumor [17,18]. Increased public awareness of the long-term sequelae of axillary dissection and the lack of evidence to support a survival advantage of axillary dissection have also contributed to this trend toward elimination of this procedure.
Perhaps the most exciting new development in the surgical management of invasive breast cancer is the emergence of sentinel lymphadenectomy and its potential to provide accurate prognostic information for the patient with breast cancer without the sequelae of an axillary dissection.
This chapter will review the history of breast sentinel lymphadenectomy, the various techniques used to identify the sentinel node, the histopathological workup of the sentinel node, the strengths and weaknesses of this technique, and its future goals.
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