Molecular classification and clinicopathological features of grade 3 endometrioid endometrial carcinoma

Purpose: This study investigates the molecular characteristics of grade 3 endometrioid endometrial carcinoma (EC) through immunohistochemical analysis of mismatch repair (MMR) proteins and p53, correlating molecular subtypes with clinicopathological features and survival outcomes. Materials and Methods: We retrospectively analyzed 33 patients with surgically staged grade 3 endometrioid EC. Immunohistochemical analysis was performed to assess MMR protein (MLH1, MSH2, MSH6, PMS2) and p53 expression. Cases were classified into MMR-deficient (MMRd), p53 wild-type (p53wt), and p53 abnormal (p53abn) molecular subtypes. A comparative analysis was conducted on clinicopathological characteristics and survival outcomes across molecular subgroups. Results: The molecular subtype distribution was: MMRd (36.4%), p53abn (15.2%), and p53wt (48.5%). Clinicopathological features, including age, stage, myometrial invasion, lymph node metastasis, and lymphovascular space invasion did not significantly differ across molecular subgroups. The p53abn group showed a non-significant trend toward reduced overall survival while disease-free survival was similar among the groups. Conclusion: Routine IHC assessment is a practical approach to identify molecular subtypes, particularly MMRd tumors that may benefit from immunotherapy, and p53abn tumors that may warrant intensified treatment strategies.