Objective: Frozen section is an accurate diagnostic tool with some unavoidable pitfalls in gynecologic tumors. We aimed to evaluate the diagnostic value of frozen section, and to detect the factors causing erroneous diagnosis in ovarian tumors.

Material and Method: Frozen section and paraffin section reports of 282 patients with ovarian neoplasms diagnosed between July 2006 and January 2013 in our institute were re-analyzed. Results were grouped into benign, borderline (for epithelial tumors) and malignant categories and compared between frozen section and paraffin section diagnosis, statistically.

Results: Overall diagnostic accuracy of frozen section was 96.5%. Sensitivity of frozen section for benign, borderline and malignant tumors were 97.5%, 95.8%, and 95.6% and the related specificities were 97.5%, 97.6%, and 100%, respectively. We found the lowest positive predictive value in borderline group (79.3%), all of them with mucinous type epithelium. Second frequent discordant tumor type was immature teratoma.

Conclusion: Apart from the limitations of frozen section, pathologists should be aware of the pitfalls of technique and tumor types and tend to sample from the solid areas particularly in mucinous tumors and teratomas to avoid inappropriate surgery.