A review of technical aspects of sentinel lymph node identification for breast cancer.

Abstract

The management of lymph nodes in breast cancer has undergone significant changes over the past century. In the Halsted radical mastectomy, axillary lymph nodes were removed en bloc with the breast and pectoralis muscles. After World War II, Waangensteen and others advocated removing the supraclavicular and internal mammary lymph nodes and the axillary nodes. More recently, others have suggested that removing clinically normal axillary lymph nodes is not therapeutic, so is unnecessary. But the status of the axillary lymph node basin remains the most powerful predictor of longterm survival in patients with breast cancer. Furthermore, pathologic analysis of the axillary nodes provides essential information for determining adjuvant therapies. Until recently, a level I/II axillary lymph node dissection (ALND) was the recommended method for identifying nodal metastases. But ALND is associated with numerous side effects, including arm numbness and pain, fluid collections, infections, and lymphedema. Because most breast cancer patients today do not have lymph node metastases, ALND offers no benefit, and may, in fact, do harm to many patients. Sentinel lymph node (SLN) biopsy has been proposed as a substitute for routine ALND in patients with clinically normal axillary basins. The SLN, the first node to receive primary lymphatic drainage from the breast, may be used to predict the status of the remainder of the axilla. A patient with a negative SLN biopsy may be spared the risks of unnecessary ALND. Early investigators attempted to identify the SLN using peritumoral injections of either blue dye or radioactive colloid, or both. In preliminary studies, SLN biopsy was followed by ALND to determine the accuracy of the biopsy results. SLN biopsy results are assessed by identification rates and false-negative rates. If the SLN is not identified, an ALND should be performed. So a high identification rate is desired to reduce unnecessary ALNDs. A falsenegative result in a patient with breast cancer is especially troublesome; cancerous lymph nodes can be left untreated in the axilla, and, more important, appropriate adjuvant therapy might not be implemented. Overall, identification rates and false-negative rates vary considerably among surgeons and might be related to the lack of a standardized technique to identify the SLN. Despite the widespread use of SLN biopsy, a number of technical questions remain: Where should the tracer be injected? What volume of radioactive colloid should be used? Is the use of dual agents better than a single agent? What is the value of preoperative lymphoscintigraphy? Should internal mammary lymph nodes be removed? Is filtered radioactive colloid better than unfiltered? When should the tracer agents be injected? The literature now includes several hundred publications with more than 10,000 patients undergoing SLN biopsy using various techniques. In many cases, individual authors advocate the particular technique used at their own institution. An overview analysis is limited by retrospective studies, various degrees of surgeon experience, conflicting indications for the procedure, and the evolution of technology over the past several years. Nevertheless, a critical and objective review is important to provide the practicing general surgeon guidelines for accurate SLN identification.