Optimal number of sentinel nodes after intradermal injection isotope and blue dye

Background: Sentinel node (SN) biopsy for breast cancer is becoming more common owing to its lower morbidity when compared with full axillary dissection. However, the optimal method of finding and the number of SN to be dissected are still subject to conjecture. The aim of this study was to determine the optimal number of SN required to accurately stage an axilla after the i.d. injection of isotope and blue dye. Method: Prospective data from all patients undergoing SN biopsy from April 2000 to September 2004 were analysed. For positive SN, the order in which they became positive was then tabulated. Results: During the 4 years, 113 patients who fulfilled the selection criteria had undergone SN biopsy with 216 SN harvested. Of these, 33 patients had positive SN results. If only the first SN was analysed, 87.9% of those positive biopsies would have been discovered. Two SN raised the predictive value to 97.0%. Conclusion: Two SN would seem to be the optimal number to harvest after i.d. injection of both isotope and blue dye.