Molecular subtyping and POLE mutation spectrum in endometrial carcinoma.

Background and objectives Endometrial carcinoma is the most common gynaecological malignancy and an emerging global health concern with limited molecular data from Indian cohorts. Our study investigated the molecular subtypes and POLE gene mutation spectrum in the South Indian cohort. Methods Molecular subtyping was carried out using ProMisE classification, categorising patients into four molecular subgroups. This involved immunohistochemistry for mismatch repair proteins, p53abn, and Sanger sequencing for POLE mutations. POLE variants were further classified, and the pathogenicity was evaluated using in silico tools. Results Histopathology presented endometrioid carcinoma in 84.9% (n= 45) cases in our study. Molecular classification revealed POLE ultra-mutated (3.8%, n=2), MMR-deficient (18.9%, n=10), p53-abnormal (17.0%, n=9), and NSMP (37.7%, n=20) subgroups. POLE gene sequencing identified 11 exonuclease domain variants, including the recurrent endometrial carcinoma hotspot V411L (3.8% ,n=2) and ten non-hotspot variants such as T323I, T457M, T466I, V460M, L306P, P441S, A465V, T290I, E321K, and T278A (22.6%, n=12). Among these, six variants T466I, V460M, L306P, P441S, T290I, and E321K were unique in our cohort, and V460M, P441S, T290I, and E321K were predicted to have oncogenic potential. Clinically, p53abn tumours showed an aggressive phenotype with higher rates of advanced-stage disease and chemotherapy use (55.6%, n=5) compared with POLE-mutated (n=0), Mismatch repair-deficient (MMRd) (37.5%, n=3), and no specific molecular profile (NSMP) tumours (10.0%, n=2). Interpretation and conclusions This study demonstrates that integrating molecular profiling with histopathology to develop clinically applicable assays strengthens endometrial carcinoma classification and improves routine prognostic assessment.