Evaluation of endometrial carcinoma prognostic immunohistochemistry markers in the context of molecular classification

Molecular subclassification of endometrial carcinoma (EC) with Proactive Molecular Risk Classifier for Endometrial Cancer (ProMisE) identifies four subtypes [DNA polymerase epsilon (POLE) mutant, mismatch repair‐deficient, p53 wild‐type (wt), and p53 abnormal]. The aim of this study was to evaluate additional EC biomarkers in the context of these subtypes. Tissue microarrays encompassing 460 previously characterized ECs were assessed for L1‐cell adhesion molecule (L1CAM), progesterone receptor (PR), estrogen receptor (ER) alpha, stathmin, and phosphatase and tensin homolog (PTEN), by immunohistochemistry (IHC). Associations with clinicopathological parameters, molecular subtype, and outcomes were determined. About 413 ECs (75% endometrioid, >15% serous) had complete data. L1CAM overexpression was found in 16%, associated with older age, lower body mass index (BMI), advanced stage, grade 3 (97%), non‐endometrioid histology (84%), deep myometrial invasion, lymphovascular space invasion (LVSI), and ER‐negative, PR‐negative status. Tumours overexpressing L1CAM were associated with poor outcomes {hazard ratio (HR) [95% confidence interval (CI)] 3.35 [2.10–5.23] for disease‐specific survival [DSS], p