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.