Value of frozen section to tailor surgical staging in apparent early-stage epithelial ovarian cancer

Objective: Frozen section (FS) has been shown to have high accuracy in determining ovarian malignancy. However, its utility in guiding surgical approaches, particularly, lymph node staging, for early-stage epithelial ovarian cancer remains unclear. This study aimed to evaluate the post-test positive probability of FSs in identifying cases requiring lymph node or peritoneal staging. The secondary aims were sensitivity, specificity, and accuracy assessments. Methods: This retrospective study analyzed patients undergoing surgery for early-stage epithelial ovarian cancer with FS performed on ovarian masses between July 2007 and March 2023 at a tertiary center. The FS results were compared with the final histology (gold standard paraffin sections). The FS cases were categorized based on further actions as follows: lymph node staging (type A), peritoneal staging only (type B), or no additional procedures (type C). The patients were divided into group 1 (requiring lymph node and peritoneal staging) and group 2 (requiring only peritoneal staging). A comparison between specialized and general pathology diagnoses was also performed. Incorrect FS assessments were classified as under-diagnosed or over-diagnosed. Results: Of the 715 patients, group 1 had appropriate staging in 425 of 447 cases, with 4.9% over-treatment. In group 2, staging was correct in 109 of 195 cases, with 44.1% under-treatment. For type A FSs, the post-test positive probability was 95% (95% CI 93% to 97%), with sensitivity, specificity, and accuracy rates of 76.4%, 86.1%, and 78.6%, respectively. For type B FSs, the post-test positive probability was 56% (95% CI 50% to 61%), with sensitivity, specificity, and accuracy rates of 68.6%, 84.5%, and 81%, respectively. There was no significant difference in the agreement between the specialized and general pathology groups (p = 0.92). Conclusions: Frozen sections suggestive of a cancer diagnosis requiring peritoneal and lymph node staging in a population with apparent early-stage epithelial ovarian cancer are highly reliable. In the case of FSs suggesting only peritoneal staging, malignancy is frequently underestimated.