Sentinel lymph node biopsy in breast cancer: an analysis of the maximum number of nodes requiring excision.

Sentinel lymph node biopsy (SNB) is now the standard of care in assessment of patients with clinically staged T1-2, N0 breast cancers. This study investigates whether there is a maximum number of sentinel lymph nodes (SLN) that need to be excised without compromising the false-negative (FN) rate of this procedure. Data were prospectively collected for 319 patients undergoing SNB between February 2001 and December 2006 at our institution. This data were analysed, both in terms of the order of SLN retrieval and relative isotope counts of the SLNs, in order to determine the maximum number of SLNs that need to be retrieved without increasing the FN rate. Furthermore, we investigated the relationship between SLN blue dye concentration and the presence of SLN metastases. The SLN identification rate was 97% with no false-negative cases amongst patients undergoing simultaneous axillary clearance historically during technique validation. In patients with SLN metastases, excision of the first 4 SLNs encountered results in the identification of a metastatic SLN in all cases. Although the majority (86%) of SNB metastases are in the hottest node, the SLN containing the metastasis is in the first 4 hottest nodes in 99% of patients with nodal metastases. The remaining 1% of SLN metastases were identified by blue dye. There was no statistically significant association between the SLN blue dye concentration and the presence of SLN metastases. A policy to remove a maximum of four blue and/or hot SLNs along with any palpably abnormal lymph nodes does not result in an increased false-negative rate of detection of SLN metastases.