Intra-operative assessment of axillary sentinel lymph nodes by frozen section-an observational study of 260 procedures.

Background: Sentinel lymph node biopsy (SLNB) has become the standard treatment for patients with invasive breast cancer. Intra-operative frozen section allows for the detection of nodal metastases, thereby allowing a simultaneous axillary lymph node dissection (ALND) for those patients with nodal metastases. We herein report the accuracy of frozen section in the detection of SLN metastases.

Methods: Patients with operable breast cancer and clinically negative axillae were recruited for SLNB. The SLNs were identified by blue dye, an isotope, or a combination. Enlarged lymph nodes that were not SLNs were also excised. All nodes were examined by intra-operative frozen section. ALND was performed if frozen section was positive. For those without metastases on frozen section, ALND was not performed. All lymph nodes underwent further paraffin sectioning with immuno-histochemical staining.

Results: A total of 260 SLNB procedures were performed for invasive carcinoma over a 3-year period. The SLN was identified in 93.5% of patients. Of the 243 successful procedures, 53 had nodal metastases on frozen section. A total of 33 patients had false-negative frozen sections (false-negative rate, 38.4%), and 97% of them were less than 2 mm in size. The false-negative rate for macro-metastases, micro-metastases, and isolated tumour cells_were 2.4%, 57.7%, and 94.4%, respectively (p < 0.0001). A total of 22 patients had delayed ALND, and the re-operation rate was 8.5%.

Conclusion: Frozen section was useful for the detection of nodal metastases in the SLNs and allowed for ALND to be performed in the same operation. The main failure of frozen sections was in the detection of micro-metastases.