The Usefulness and Limitations of Intraoperative Frozen Section Analysis of Sentinel Lymph Nodes in Patients with Breast Cancer

Purpose: Intraoperative frozen sectioning (FS) of sentinel lymph nodes (SLNs) is widely used to determine whether total axillary lymph node dissection should be performed in patients with breast cancer. We evaluated the usefulness and limitations of the FS protocol, which has been used in our institution for the intraoperative SLN examination. Methods: We analyzed the FS results of SLNs in 807 invasive breast carcinoma patients who underwent intraoperative SLN biopsy between January 2005 and December 2007. Lymph nodes larger than 5 mm were sliced at 2 mm intervals and all the slices were submitted for FS. The remaining tissue of the SLN was formalin-fixed and paraffin-embedded for permanent sectioning (PS). If the FS result was negative for tumor cells, then immunohistochemical stain for pancytokeratin was performed. The metastatic SLNs were graded according to the AJCC cancer staging manual (6th edition). The results of FS and PS were compared with regard to the pathologic diagnosis. Results: The average number of SLNs was 2.9 per patients. A total of 204 (25.3%) patients were reported to have a metastatic SLN(s) on the FS. Among the 603 patients with negative FS results, 34 (5.6%) patients showed metastasis on the PS. Another 10 (1.7%) patients who had negative results on FS showed isolated tumor cells on the PS or on the cytokeratin immunohistochemistry. Twenty-nine of the 34 (85.3%) false negative cases showed micrometastasis on the PS. Ten (29.4%) false negative results were caused by interpretation errors and 24 (70.6%) were caused by technical problems. Conclusion: The false negative rate of our protocol for FS of a SLN was low. The failure of FS was largely caused by the failure to detect micrometastasis. FS is a reliable method for an intraoperative SLN examination if a very stringent protocol is used.