Intra-operative margin assessment in extra-mammary Paget's disease of the vulva: accuracy and impact on surgical outcomes.

OBJECTIVE: Extra-mammary Paget's disease of the vulva is a rare intra-epithelial malignancy characterized by high recurrence rates, largely attributable to microscopic extension beyond clinically apparent margins. The objective of this study was to evaluate the discriminatory performance of intra-operative frozen-section sampling for final margin status and to examine whether its addition after pre-operative biopsy mapping was associated with improvement in clinical outcomes such as final margin status, recurrence rate, or disease-free survival. METHODS: We conducted a retrospective cohort study of women treated with surgical excision for vulvar Paget's disease at our institution between January 2014 and December 2024. Intra-operative frozen-section findings were compared with definitive histopathologic margin status. Clinical outcomes, including recurrence rate, disease-free survival, and anatomical site of recurrence, were analyzed. RESULTS: A total of 66 patients were included, and intra-operative frozen-section margin assessment was performed in 55 cases (83.3%). Among the 55 patients who underwent intra-operative frozen-section assessment, 37 (67.3%) had at least one positive frozen-section margin and consequently underwent an additional excision. Despite these additional resections, 67.6% of these patients still had positive margins on the final histopathologic specimen. Notably, even among the 18 patients with negative intra-operative margins, definitive histology demonstrated positive margins in 72.2% of cases. Intra-operative frozen-section assessment showed an overall accuracy of 54.5% (95% confidence interval, 40.6% to 68.0%). Disease recurrence occurred in 23 patients (34.8%), and the development of recurrence was not significantly associated with intra-operative frozen-section assessment (p = .171). CONCLUSIONS: Among patients undergoing surgery for vulvar Paget's disease, after pre-operative biopsy mapping, the addition of intra-operative frozen-section sampling did not demonstrate a significant improvement in final margin status or disease recurrence. These findings do not provide evidence supporting the routine addition of frozen-section sampling to pre-operative mapping, while its use may be reserved only for selected clinical scenarios.