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Breast cancer patients undergoing a mastectomy or breast-conserving procedure are candidates for axillary sentinel lymph node dissection 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 sentinel lymph node dissection and standard axillary lymph node dissection in finding positive lymph nodes is quite high (95%) in the hands of experienced surgeons. Although at least one sentinel lymph node can be identified in the majority of cases, in a small percentage, identification may not be possible, necessitating complete axillary node dissection. In addition, a false-negative finding occurs in 3%–10% of the patients having sentinel lymph node dissection—that is to say, the sentinel nodes are negative, but higher nodes are found to be positive. The advantages of sentinel lymph node dissection are fewer complications versus axillary lymph node dissection and the ability to identify sentinel lymph nodes that are not in the traditional level I or II areas. Identification of sentinel lymph nodes focuses on the histopathologic examination, which may include immunohistochemical staining as well as the traditional hematoxylin and eosin staining. The importance of micrometastases (<2 mm) is under study, but the total number of nodes involved with metastases may influence the adjuvant therapy that is offered. Contraindications to sentinel lymph node dissection include suspicious, palpable axillary lymphadenopathy and regional breast operations (e.g., breast reduction) that alter normal lymphatic flow. Sentinel lymph node biopsy may be considered after prior axillary surgery, but lymphatic mapping may be necessary to identify alterations in drainage patterns, and the identification rate of sentinel nodes may be lower.
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PREOPERATIVE PREPARATION
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The skin should be free of infection, as should the preceding breast biopsy site. The preparation, delivery, and monitoring of the radionuclide solution for injection must be coordinated with the nuclear medicine staff.
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General anesthesia with endotracheal intubation is preferred because some patients will also have axillary lymph node dissection and may be having a concurrent operation on the breast. Most surgeons prefer that the anesthesiologist uses a short-acting muscle-paralyzing agent for placement of the endotracheal tube such that the motor nerves can still be identified with mechanical stimulation during the axillary lymph node dissection.
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Patients are placed in a comfortable supine position with the arm out at 90 degrees on a padded arm board (FIGURE 1). This position allows easy access to the breast and axilla. Some surgeons prefer to wrap the arm, ...