Endometrial thickness in patients with postmenopausal bleeding and endometrial cancer: A retrospective cohort study

Updated ACOG guidelines recommend a combined approach of transvaginal ultrasound (TVUS) and endometrial sampling for evaluation of most postmenopausal bleeding (PMB). Although prior studies investigating the reliability of TVUS suggest that non-endometrioid endometrial cancer subtypes present with thinner endometrium, some included cases with incomplete endometrial visualization. We therefore evaluated endometrial thickness (ET) by cancer subtype while controlling for incomplete endometrial visualization.

We performed a retrospective cohort study of patients with PMB who underwent TVUS followed by tissue-confirmed endometrial cancer at three academic centers (2013-2022). Cancers were classified as endometrioid or non-endometrioid (serous, clear cell, carcinosarcoma, undifferentiated). Fibroid presence, endometrial visualization, and race/ethnicity were recorded. Patients with incomplete endometrial visualization were excluded from endometrial thickness analysis. Appropriate nonparametric statistical comparisons were performed.

Among 171 analysis-eligible patients (121 endometrioid, 50 non-endometrioid), non-endometrioid cancers were more common among non-Hispanic Black (53%) than non-Hispanic White (20%) or Hispanic patients (25%). Patients with non-endometrioid cancers were more likely to have incompletely visualized endometria (34% vs 9.1%, p < 0.01). Among patients with complete visualization, mean ET did not differ between endometrioid and non-endometrioid cancers (16.9 vs 19.5 mm) or by race/ethnicity. ET ≤4 mm occurred in 5.6% of cancers with fully visualized endometria, without differences between subtypes.

When endometrium was fully visualized, non-endometrioid cancers did not present with thinner ET than endometrioid cancers, and a 4 mm cutoff may miss 5.6% of cancers. Incomplete visualization, more common in non-endometrioid disease, may lead to additional missed diagnoses, supporting universal endometrial sampling for PMB.