Introduction Serous tubal intraepithelial carcinoma (STIC) are precursors for high grade serous carcinomas (HGSC) of tubo-ovarian origin. It is most commonly encountered during risk-reducing surgery for patients with a BRCA germline pathogenic variant (PV). An isolated STIC at risk-reducing surgery is associated with a 27.5% risk of primary peritoneal HGSC at 10 years. There is little known about the risk of subsequent HGSC in an average risk patient found to have an isolated STIC. The objective of this study is to explore the outcomes of STIC diagnosed in a population of patients without a known hereditary mutation at the time of surgery.

Methods Retrospective population based cohort study from British Columbia, Canada. Chart review of patients with an isolated STIC from January 2012 to May 2022. The estimated population prevalence of STIC, and outcomes including subsequent HGSC and BRCA mutations are described.

Results Twenty nine patients were identified, including 20 patients with no known BRCA PV (‘average risk’) undergoing primary surgery for non-risk reducing indications. The estimated prevalence of STIC in this population was 0.1%. Patients were followed for a median of 63 (9–127) months. Five of these 20 average risk patients (25%) developed HGSC at 18, 29, 70, 80, 106 months, and only 1 (5%) of these was subsequently found to have a BRCA PV.

Conclusion/Implications STIC identified in average risk population patients with negative genetic testing are still at risk of subsequent HGSC. Recommendations for STIC management should be applied to all patients regardless of BRCA status.