Comparison of diagnostic accuracy of frozen section with imprint cytology for intraoperative examination of sentinel lymph node in early-stage endometrial cancer: results of Senti-Endo study.

BACKGROUND: In early-stage endometrial cancer, intraoperative examination of sentinel lymph nodes (SLNs) can predict nodal involvement and avoid a second surgical procedure. Our goal was to determine the diagnostic accuracy (DA) of intraoperative examination in diagnosing metastatic pelvic SLNs.
METHODS: This was a retrospective study, including 125 patients with early stage endometrial cancer. Results of intraoperative examination by frozen section (FS) or imprint cytology (IC) were compared with final histology (serial sectioning and immunohistochemistry (IHC)). The diagnostic value of intraoperative examination was calculated.
RESULTS: Of the 111 patients with SLNs detected (89%), 87 (78.5%) had an intraoperative examination (30 with FS and 57 with IC). Intraoperative examination detected SLN metastases in 9 of 16 patients with metastatic SLN at definitive histology (sensitivity = 56.3%): macrometastasis in 8 and micrometastasis in 1. Seven false-negative cases were found (43.7%; micrometastases in 6 and isolated tumor cells in 1). The DA of intraoperative examination was 92% (95% confidence interval (CI), 84-96.7). For FS and IC, DA was 97.3% (95% CI, 85.8-99.9) and 88% (95% CI, 75.7-95.5), respectively.
CONCLUSIONS: FS has better DA than IC for intraoperative examination of SLNs in endometrial cancer. The main limitation of both techniques is in detecting micrometastasis and isolated tumor cells.