Endometrial Mixed and Mixed-Feature Carcinomas: Small Cohort Clinicopathologic and Molecular Studies.

To examine the clinical, pathologic, and molecular features of mixed and mixed feature endometrial carcinomas and compare them to pure serous carcinoma and pure endometrioid carcinoma. The study analyzed the clinical characteristics, histologic composition, and molecular genetic profiles of mixed and mixed feature endometrial cancers, with a focus on shared and distinct mutations. Patient demographics, disease-free survival, and molecular alterations, including in TP53, PIK3CA, TERT, MAP2K1 genes, and ERBB2 gene amplifications, were assessed and compared to pure serous and pure endometrioid carcinomas. Patients with mixed and mixed-feature carcinomas were older (median age: 73 years) and had worse disease-free survival (median: 23 months) than those with pure endometrioid carcinoma (median: 48 months). Mixed and mixed-feature carcinomas were histologically high-grade, most commonly comprising serous and endometrioid components. Molecular profiling supported a clonal origin of these tumors, with identical TP53 and PIK3CA gene mutations between the two histologic components in each case. There were additional gene mutations (e.g., TERT and MAP2K1) found in higher-grade components. ERBB2 amplifications were more frequent in the mixed carcinomas groups (33%) compared to pure serous (11%) and pure endometrioid carcinomas (0%). Some of the mixed and mixed-feature carcinomas also showed FBXW7 mutations, not seen in either the pure endometrioid or pure serous carcinomas. Mixed and mixed-feature carcinomas share origins with pure endometrial serous and endometrioid carcinoma subtypes but exhibit distinct molecular alterations. These findings highlight the importance of molecular subtyping for diagnosis and treatment planning. Future research could focus on larger cohorts and targeted sequencing to better understand the pathogenesis of mixed and mixed-feature carcinomas in order to refine therapeutic strategies.