Revisiting the 4 mm Endometrial Stripe Thickness Threshold for Risk Stratification of Endometrial Cancer

ABSTRACT Objective Type 2 endometrial cancer (EC) histology has been associated with endometrial stripe thickness (EST) < 4 mm, and anatomic factors like obesity, fibroids, and endometrial polyps have been found to impact sonographic interpretation of EST. We aim to evaluate the recommended 4 mm EST threshold for endometrial biopsy in patients with postmenopausal bleeding, with rising incidence of type 2 EC and high prevalence of obesity and uterine structural factors. Methods This retrospective cohort study identified patients with EC at an academic center (October 2015 to December 2017), abstracting demographic data, EST measurement, presence of fibroids or endometrial polyps, EC histology, grade, and stage at diagnosis. χ 2 tests and logistic regression were performed comparing EST ≤ 4 and > 4 mm groups. Results 445 patients were included after application of the inclusion/exclusion criteria. Type 1 EC accounted for 83.9% and type 2 for 16.1%. About 8% had EST ≤ 4 mm. Type 2 histology was associated with a higher proportion of EST ≤ 4 mm than type 1 (15.7% vs 6.8%, p = 0.029). Lower BMI was associated with increased odds of EST ≤ 4 mm; OR 5.42 for BMI < 25 versus BMI ≥ 40 kg/m 2 (95% CI 1.29‐22.90, p = 0.021). There was no association of fibroids or polyps with EST. Conclusions Type 2 EC and lower BMI were associated with EST ≤ 4 mm. The 4 mm EST threshold does not consider cancer histology or factors that impact sonographic interpretation; this threshold should be re‐evaluated, as the current guidelines may put some patients at risk of delayed diagnosis.