Diagnostic Accuracy of Intraoperative Frozen Section and Causes of Error in Ovarian Epithelial Tumors: An Institutional Experience

Background: Ovarian cancer is the second most common type of female genital tract malignancy. Treatment planning differs for benign, borderline, and malignant subtypes of surface epithelial tumors and depends on accurate histopathological diagnosis. The aim of this study is to determine the accuracy and causes for error in intraoperative diagnosis of ovarian surface epithelial tumors.Methods: In this retrospective study, we analyzed all cases of ovarian surface epithelial tumors referred to the Pathology Department of our hospital from April ۲۰۱۰ to December ۲۰۱۵. We considered the final diagnosis as the gold standard and determined the accuracy, sensitivity, specificity, positive predictive value, negative predictive value, underdiagnosis and overdiagnosis for each group of benign, borderline, and malignant tumors. An expert pathologist blinded to the diagnosis reviewed patients’ frozen and permanent slides and categorized causes of error into misinterpretation, sampling, and technical errors.Results: We assessed ۲۲۰ patients’ slides (۹۶ benign, ۶۶ borderline, and ۵۸ malignant tumors). The accuracy of the frozen section was: ۹۸% in benign, ۸۰.۳% in borderline and ۶۷.۲% in malignant tumors. The frozen sections had a sensitivity of ۹۷.۹% for benign tumors and a sensitivity of ۶۷.۲% and specificity of ۱۰۰% for malignant tumors. Borderline tumors had a sensitivity of ۹۱% and specificity of ۸۸.۴%. Mucinous borderline tumors comprised the more frequent uncertain and underdiagnosed cases. The main cause for error in this group was sampling error. In malignant neoplasms, ۱۵.۵% were reported to be at least borderline. Technical issues were the cause of difficulty in interpretation. In the benign category, cystadenofibroma could be misinterpreted as a borderline malignancy.Conclusion: Frozen section is an accurate, specific method for diagnosis of benign and malignant tumors. In the borderline category, the results should be interpreted with caution.