Clinicopathological characteristics and prognostic analysis of synchronous endometrioid endometrial and ovarian carcinomas: a retrospective cohort study

BACKGROUND: Synchronous endometrioid endometrial and ovarian carcinomas (SEEOCs) represent a small yet clinically significant entity of gynecological malignancies. Their clinicopathological correlations, immunohistochemical profiles, and prognosis have not been well established. METHODS: We conducted a retrospective analysis of 50 SEEOC cases identified among 1160 patients with endometrioid endometrial carcinoma at a single institution. Clinicopathological parameters, including immunohistochemical profiles, were evaluated. Progression-free survival (PFS) was analyzed, with Kaplan-Meier analysis performed to identify significant prognostic factors. RESULTS: Deficient mismatch repair (dMMR) was detected in 36.1% of SEEOC cases and mutant p53 expression in 13.2%. PD-L1 (22C3) positivity was observed in 63.0% cases, and HER2 expression in 75.0%. Factors associated with worse PFS included poor tumor differentiation, > 50% myometrial invasion, lymphovascular space invasion (LVSI), lymph node metastasis, and advanced 2023 FIGO stage. Kaplan-Meier pairwise comparisons revealed that patients with focal LVSI had a PFS comparable to that of patients with substantial LVSI. Five patients were classified as FIGO IA3 stage. All patients at IA3 stage were premenopausal, showed no MELF (microcystic, elongated, and fragmented) invasion pattern, and none had recurrence. CONCLUSIONS: These findings support the prognostic significance of poor tumor differentiation, > 50% myometrial invasion, LVSI, lymph node metastasis, and 2023 FIGO staging system in SEEOCs. The high rates of dMMR, HER2, and PD-L1 positivity in SEEOCs suggest potential for targeted therapies in future therapeutic strategies.