Sentinel lymph node biopsy for breast cancer: how many nodes are enough?

Introduction: Sentinel lymph node (SLN) biopsy using blue dye and radioisotope often results in the removal of multiple SLNs. We sought to determinewhether there is a point where the surgeon can terminate the procedure without sacrificing accuracy. Methods: One thousand one hundred ninety-seven patients from University of Michigan and the Mayo Clinic undergoing SLN biopsy formed the study population. Surgeons removed all SLNs until counts within the axilla were less than 10% of the highest node ex vivo and recorded the order in which they were removed. Results: The mean number of SLNs removed per patient was 2.5 (range 1‐9). Approximately 42% of patients had three or more lymph nodes removed, while 19% had four or more lymph nodes removed. Eighteen percent of patients (132/725) at University of Michigan and 22% (103/472) at Mayo Clinic had a positive SLN. Ninety-eight percent (231/235) of patients with lymph node metastases were identified by the 3rd SLN while 100% were identified by the 4th SLN. Conclusion: Among patients undergoing SLN biopsy for breast cancer, the only positive SLN is rarely identified in the 4th or higher node. Terminating the procedure at the 4th node may lower the cost of the procedure and reduce morbidity. J. Surg. Oncol. 2007;96:554–559. 2007 Wiley-Liss, Inc.