Sentinel lymph node biopsy: technique validation at the Setúbal Medical Centre, Portugal

AIMS: To evaluate the accuracy of sentinel lymph node biopsy in breast cancer patients at this institution, using combined technetium-99m ((99m)Tc) sulphur colloid and patent blue vital dye. METHODS: From March 2007 to July 2008, 50 patients with a tumour of less than 3 cm and with clinically negative axillary lymph nodes underwent sentinel lymph node biopsy (SLNB), followed by axillary lymph node dissection (ALND). Sub-areolar (99m)Tc sulphur colloid injection was performed the day before surgery, and patent blue vital dye was also injected sub-areolarly at least 5 minutes before surgery. Sentinel lymph node was identified during the surgical procedure, using a gamma probe and direct vision. All sentinel nodes underwent frozen section analysis. Later haematoxylin and eosin staining and immunohistochemical analysis were performed. Finally, SLNB was compared with standard ALND for its ability to accurately reflect the final pathological status of the axillary nodes. RESULTS: The sentinel lymph node (SLN) was identified in 48 of 50 patients (96%). The number of sentinel lymph nodes ranged from one to four (mean 1.48) and non-sentinel nodes ranged from seven to 27 (mean 14.33). Of the 48 patients with successfully identified SLNs, 29.17% (14/48) were histologically positive. Sensivity of the SLN to predict axilla was 93.75%; accuracy was 97.96%. The SLN was falsely negative in one patient—6.25% (1/16). CONCLUSIONS: The SLNB represents a major advance in the surgical treatment of breast cancer as a minimally invasive procedure predicting the axillary lymph node status. This validation study demonstrates the accuracy of the SLNB and its reasonable false negative rate when performed in our institute. It can now be used as the standard method of staging in patients with early breast cancer at this institution.