Accuracy of frozen section at early clinical stage of endometrioid endometrial cancer: a retrospective analysis in Germany

PURPOSE: The aim of this study was to estimate the accuracy of intra-operative frozen section (FS) diagnosis during hysterectomy for early-stage endometrial cancer (EC).

METHODS: At the Department of Obstetrics and Gynecology, University of Luebeck, between 2009 and 2014, the intra-operative FS pathology of 164 patients with pre-operative endometrial curettage, showing G1 or G2 endometrioid EC at an early clinical stage (FIGO I-II), was compared retrospectively with the final paraffin section reports. The accuracy of myometrial invasion (MI) in all patients and separately in stage FIGO I patients was calculated and the under- or overtreatment of the patients was analyzed. A subgroup analysis was performed focusing on the percentage of inadequate staging by FS with clinical consequences.

RESULTS: Concordance of FS and final pathology results in terms of FIGO stage was 85.2%, with an under-diagnosis rate of 14% and an over-diagnosis rate of 0.8%. The subgroup analysis rate of patients who were inappropriately operated using FS was 6.6%, while 3.3% underwent a secondary operation. The overall accuracy of FS in predicting MI was 93.3% and in patients with stage FIGO I, 92.7%. Sensitivity, specificity, PPV and NPV were 98.25%, 89.06%, 88.89% and 98.28%, respectively, and in stage FIGO I, 98.25%, 84.62%, 90.32% and 97.06%, respectively.

CONCLUSION: The authors consider that intra-operative FS is a reliable diagnostic method to identify the clinical stage of EC and especially MI, to determine the necessity of lymphadenectomy. Further development of diagnostic techniques is essential to maximize diagnostic accuracy.