Clinical implications of morular metaplasia in fertility-preserving treatment for young patients with endometrial hyperplasia and atypical endometrial hyperplasia: a retrospective cohort study

Objective To evaluate the clinical significance of morular metaplasia (MM) and its temporal patterns in predicting outcomes of fertility-preserving treatment (FST) among young patients with endometrial hyperplasia (EH) and atypical endometrial hyperplasia (AEH). Design Retrospective cohort study. Subjects 193 patients aged <40 years with EH or AEH who received progestin-based FST (2020–2025) at a single tertiary hospital. Exposure MM classified as: MM‑Bef (present only before treatment, n = 9), MM‑Sus (persistent, n = 4), MM‑Aft (emerged after treatment, n = 11), and non‑MM (n = 169). Main outcome measure(s) Complete response (CR) rate, time to response (TTR), and factors associated with CR by Cox regression. Result Overall CR was 62.5% in MM vs. 69.8% in non‑MM (P = 0.485). MM‑Bef achieved 100% CR, MM‑Sus 50%, MM‑Aft 36.4% (MM‑Aft vs. non‑MM, P = 0.009). Median TTR was 5.0 vs. 6.0 months (P = 0.849). Kaplan‑Meier showed no significant difference (log‑rank P = 0.893). In univariable Cox regression, only EH diagnosis was associated with higher CR (HR=1.515, P = 0.031). MM overall or subgroups was not significant (P > 0.10). Conclusion MM is not an independent predictor of FST outcomes in young EH/AEH patients. However, temporal patterns of MM may represent potential clinically useful signals. Persistent or treatment‑emergent MM showed numerical trends toward lower response rates and longer TTR, suggesting these patients may benefit from enhanced surveillance. These hypothesis-generating findings require confirmation in larger studies.