Molecular Profiling and Treatment Outcomes in Uterine Serous Carcinoma: Prognostic Role of Estrogen Receptor Expression.

Uterine serous carcinoma (USC) represents a rare but aggressive subtype of endometrial cancer, accounting for a disproportionate number of disease-related deaths. Although molecular classification has improved risk stratification, prognostic heterogeneity highlights the need for new prognostic markers. We retrospectively analyzed 83 patients with USC treated at our institution between 1 January 2015 and 31 December 2023. Clinicopathological characteristics, treatment strategies, molecular biomarkers accessed by immunohistology (TP53, ER, PR, HER2, and MMR status), and survival outcomes were collected. Patients were first staged by FIGO 2009 and retrospectively reclassified by FIGO 2023. Disease-free survival (DFS), progression-free survival (PFS), and overall survival (OS) were assessed using Kaplan-Meier and Cox regression analyses. The majority of patients were presented with advanced disease (FIGO stage IIIC-IV). TP53 mutations were found in 88% of cases, HER2 amplification in 18%, and ER expression in 57.8%. ER-positive patients showed significantly improved DFS in the adjuvant setting compared with ER-negative patients, whereas no significant associations were observed for first-line PFS or OS in multivariable analyses. HER2 amplification was not associated with inferior survival in our cohort. The advanced stage remained an independent predictor of worse OS. USC is a biologically heterogeneous disease, and its treatment should be guided by its molecular profile. ER expression identifies a subset of patients with improved DFS, suggesting potential prognostic relevance in this high-risk histology.