Aim of the study: Intraoperative frozen section (FS) examination of the Sentinel node (SN) in breast cancer patients is questioned due to the relatively high number of positive SN(s) found in the permanent histological examination. This study reviews the data of the Austrian sentinel node study group on FS examination of the SN and tries to identify patients with a high risk of incorrect negative results. Methods: 2326 breast cancer patients of the Austrian Sentinel node study group who underwent SN biopsy and intraoperative FS examination of the SN were further analysed for incorrect negative results and clinicopathologic factors indicating a higher rate of incorrect negative results. Results: The FS of the SN was positive in 513 of 2326 patients (22.1%) and negative in 1813 of 2326 patients (77.9%). Permanent histological examination revealed a metastatic SN in 282 of 1813 patients. (incorrect negative rate 15.6%). 158 of 282 patients (56%) were found through H&E serial sectioning, whereas 124 of 282 patients (44%) were only seen in immunohistochemistry. Micrometastases, lobular histology and preoperative chemotherapy were associated with a higher rate of incorrect negative results. Conclusion: Incorrect negative results of FS examination are seen in 15% of patients and require a secondary axillary lymph node dissection. The disadvantage of missing a positive SN through FS is by far outweighed by the advantage of a single stage operation in case of a positive SN.

        Key words: sentinel node biopsy – breast cancer – frozen section – incorrect negative results