Introduction/Background Surgical staging in apparent early-stage epithelial ovarian cancer(ES-EOC) requires peritoneal and lymph node assessment; however, in some histological subtypes the indication for lymph node staging(LNS) may be questioned. Previous studies on frozen section(FS) have reported high overall accuracy in determining malignancy of ovarian masses. Nevertheless, data on the value of intra-operative FS to plan the correct surgical strategy in ES-EOC is scanty .

Primary and secondary endpoints were to assess the role of FS in identifying cases requiring peritoneal and LNS and peritoneal staging only respectively.

Methodology Retrospective, tertiary single-center study. Patients undergoing primary surgery with final histology of ES-EOC and FS performed on the ovarian mass between July2007 and March2023 were included. FS was compared with gold standard paraffin section. Patients were divided according to the need of receiving LNS or not. Sensitivity, specificity, accuracy, likelihood ratio and post-test probability were analyzed for the need to perform LNS.

Results 715 patients were included. The sensitivity, specificity and accuracy of FS versus LNS were 76.4%, 86.2% and 78.6% respectively. False negatives were 131 out of 556(23.6%). Positive likelihood ratio was 5.52(95%CI= 3.74–8.16). The probability of performing correct LNS after FS reporting ‘high grade’or’carcinoma’ was 95%(95%CI=93–97%). The sensitivity, specificity and accuracy of FS versus peritoneal staging only were 68.6%, 84.5% and 81% respectively. False negatives were 50 out of 159(31.4%). Positive likelihood ratio was 4.43(95%CI= 3.55–5.53). The probability of treating an ES-EOC properly after FS reporting diagnosis requiring peritoneal staging only was 56%(95%CI=50–61%).

Conclusion Patients with FS reporting for suspected ovarian carcinoma requiring LNS, have high probability to be adequately staged, but risk of false negatives is 23.6%. When FS reports for a diagnosis requiring peritoneal staging only(no intra-operative need of LNS), patients undergo inadequate surgical staging in 44% of the cases. Underestimation of malignancy is observed, but overestimation seems less common.

Disclosures Nothing to disclose.