Evaluation of the Two Intraoperative Examination Methods for Sentinel Lymph Node Assessment: A Multicentric and Retrospective Study on more than 2,000 Nodes

Background: Intraoperative frozen section (FS) and imprint cytology (IC) are currently used to detect sentinel lymph node (SLN) metastasis, allowing for complete dissection when necessary. Materials and Methods: A 2-year retrospective chart review was performed for patients who underwent SLN procedure in five French hospitals. The FS and IC results were compared to the definitive histology in order to calculate the sensitivity, specificity and false-negative rate. These results were studied from both the surgeon's and the pathologist's point of view. Results: The comparison of the FS group (n=672) and IC group (n=576) showed a lack of sensitivity for both techniques, even if it was better for FS (59.3% vs. IC=33.3%). The false-negative rate (among patients with metastases) was very high in the two groups (FS=40.7% vs. IC=66.6%), leading to high re-intervention rates (FS=40.7% vs. IC=30.2%). False-negative nodes were more often small metastases and lobular carcinoma type. Conclusion: The interest in intraoperative examination is questionable. To avoid intraoperative examination failures, we think that complete staging of the disease before surgical treatment would be more relevant.