To analyze the clinical and pathological features of asymptomatic postmenopausal women with an incidentally detected increase in endometrial thickness (ET) by transvaginal ultrasound examination and discuss the cutoff value of ET for the timely discovery of endometrial malignancy.This was a retrospective study of postmenopausal women with asymptomatic thickened endometrium (greater than or equal to 5 mm) screened by transvaginal ultrasound who were referred to the gynecology department at Xuanwu Hospital between January 2018 and March 2021. Data on participant demographics, clinical characteristics, and histopathology outcomes were collected. We stratified the participants into the benign group and malignant group according to pathology results and assessed differences between the two groups. A receiver operating characteristic curve was used to identify the cutoff value of ET for predicting endometrial malignancy in postmenopausal women with asymptomatic thickened endometrium.A total of 163 eligible cases were included in the analysis. The results showed that only ET was significantly different between the two groups. The median ET was significantly higher in the malignant group than in the benign group (1.20 vs 0.80, P = 0.023). The optimal cutoff value of ET was 10 mmwith the maximum AUC (0.881, 95% CI 0.810-0.952, P = 0.024), and the sensitivity and specificity for the diagnosis of endometrial malignancy were 100%and 80%, respectively. Among the 47 women with ET ≥ 10mm, the prevalence of endometrial malignancy was 6.3%, which was significantly higher than that among women with ET < 10mm ( P = 0.023).For postmenopausal women with asymptomatic endometrial thickening, the prevalence of endometrial malignancy is significantly higher when ET is ≥ 10 mm. If ET is ≥ 10mm, further histopathological testing should be recommended to exclude endometrial malignancy. Further large-sample and prospective studies are needed to determine the predictive value of ET.Copyright © 2022 by The North American Menopause Society.