Reliability of frozen section in breast sentinel lymph node examination

Sentinel lymph node (SLN) examination in breast carcinoma is crucial to spare patients unnecessary lymph node (LN) dissection. The specificity and accuracy of SLN examination by frozen section has been variable in many studies. This study aims to describe our experience in frozen section (FS) analysis of SLN. We have retrospectively analyzed data from 449 axillary SLN subjected to FS examination from 440 patients with breast cancer. All patients had free axillary LN clinically. Out of 449 cases, no false positive cases were found on FS (specificity of 100 %). Twenty-six cases were false negative (6 interpretation-related reasons and 20 technical-related reasons). The overall sensitivity was 84 % with a total accuracy rate of 93 % and interpretation sensitivity of 96 %. Three cases were deferred. Twenty-two of the false negative cases were micrometastases, whereas 4 were macrometastases. The interpretation-related false negative cases were not related to the subtype of carcinoma (ductal vs. lobular). However, they were all of low nuclear grade. These findings are similar to most published data. FS is a reliable method for evaluating SLN. The most common cause of false negative diagnosis is sampling error. More attention should be paid to low-grade tumors. Moreover, in FS analysis, we recommend to totally submit SLNs that are less than 5 mm in diameter, bisecting them if possible, and to serially section SLNs that are at least 5 mm at 2-mm intervals.