BACKGROUND:Intraoperative pathological assessment is frequently requested in patients with suspected ovarian neoplasia so that optimal surgical management can be performed. In this study the accuracy of intraoperative cytology has been assessed and the results compared with frozen section diagnosis.METHODS:The study comprised 402 ovarian tumors that were submitted for intraoperative assessment in which both cytology preparations, usually scrape smears, and conventional frozen sections were examined. Each technique was evaluated independently, although the diagnosis transmitted to the surgeon was based upon the combination of the clinical, macroscopic, histological, and cytological information. The results were compared with the final pathological diagnosis in each case and cases with discordant diagnoses were reviewed.RESULTS:There were 226 benign lesions, 35 borderline epithelial neoplasms, and 141 malignant tumors according to the final pathological diagnosis. All benign lesions were accurately categorized using both frozen section and cytology. Thirty (86%) of the borderline tumors and 137 (97%) of the malignant tumors were accurately identified on frozen section, whereas the corresponding results for cytology were 23 (66%) and 131 (93%), respectively. There were no false‐positive diagnoses with either technique and the overall accuracy was 97.8%. Cytological evaluation provided better morphologic detail, permitted wider tumor sampling, and directed appropriate ancillary investigations in some cases.CONCLUSIONS:Overall, frozen section was more accurate than smear preparations in this series. However, cytology has a complementary role in the intraoperative assessment of ovarian neoplasia and provides a more specific diagnosis in some cases. Cancer (Cancer Cytopathol) 2010. © 2010 American Cancer Society.