Endometrial Thickness Cutoff for Postmenopausal Bleeding
In postmenopausal women with bleeding, an endometrial thickness ≤4 mm on transvaginal ultrasound has a nearly 100% negative predictive value for endometrial cancer and requires no further evaluation, while thickness ≥5 mm mandates endometrial tissue sampling. 1, 2, 3
The 4 mm Threshold: Evidence and Application
The 4 mm cutoff represents the critical decision point for postmenopausal bleeding evaluation:
Endometrial thickness ≤4 mm conveys a >99% negative predictive value for endometrial cancer, making it safe to avoid invasive sampling in this group 1, 2, 3
TVUS is the first-line screening test for endometrial cancer in postmenopausal bleeding, combining high sensitivity with non-invasive assessment 1, 2
The American College of Radiology and ACOG both endorse this 4 mm threshold as the standard of care 1, 3
When to Proceed with Tissue Sampling
Any endometrial thickness ≥5 mm in a symptomatic postmenopausal woman requires endometrial tissue sampling to exclude malignancy or hyperplasia 1, 4, 2:
Office-based endometrial biopsy using Pipelle or Vabra devices should be the initial sampling method, with sensitivities of 99.6% and 97.1% respectively for detecting endometrial carcinoma 4, 2
If office biopsy is inadequate, inconclusive, or negative but clinical suspicion remains high (especially with thickness ≥10 mm), proceed to hysteroscopy with directed biopsy 4, 5
Blind sampling techniques have a false-negative rate of approximately 10% and may miss focal lesions 2, 5
Critical Nuances and Pitfalls
The 10 mm Threshold Requires Special Attention
When endometrial thickness is ≥10 mm and initial Pipelle sampling is negative, hysteroscopic evaluation with directed biopsy is strongly recommended 5
In one study of 588 women with thickness ≥10 mm, 12.4% of endometrial cancers were missed by Pipelle but detected on hysteroscopy 5
TVUS Limitations to Recognize
TVUS cannot reliably determine the etiology of endometrial thickening—it only measures thickness, not pathology 1, 2
Abnormal echogenicity and texture of the endometrium correlate with significant pathology even when thickness appears normal 1, 2
Always combine transvaginal with transabdominal ultrasound for complete pelvic assessment 1, 2
The Conservative 3 mm Alternative
Some European guidelines (ESMO) recommend a more conservative cutoff of ≤3 mm, though this is not standard in U.S. practice 2
One study found 3 mm provided 100% sensitivity but only 13% specificity, resulting in many unnecessary procedures 6
Asymptomatic Incidental Findings
An endometrial thickness >4 mm discovered incidentally in an asymptomatic postmenopausal woman does not routinely require evaluation, though assessment should consider individual risk factors including obesity, diabetes, unopposed estrogen use, and family history 3, 7:
The threshold for asymptomatic women is higher (≤11 mm) according to some guidelines 4
TVUS is not an appropriate screening tool for endometrial cancer in asymptomatic postmenopausal women 3, 7
Adjunctive Imaging When Initial TVUS is Inconclusive
Sonohysterography (saline infusion sonography) helps distinguish focal from diffuse pathology when TVUS shows focal abnormalities 1, 4, 2
MRI with diffusion-weighted sequences may be considered when ultrasound is inadequate or findings are indeterminate, with sensitivity up to 79% and specificity up to 89% for endometrial cancer 1, 2
Color Doppler evaluation of endometrial vascularity can identify vessels within polyps or cancer 1
Clinical Risk Factors That Lower the Threshold for Sampling
Consider more aggressive evaluation even with borderline thickness in women with 3, 7, 8:
- Age >55 years
- Obesity (higher BMI correlates with cancer risk)
- Recurrent bleeding episodes
- Heavy bleeding (>5 pads per day)
- Diabetes mellitus or hypertension
- Unopposed estrogen use
- Family history of gynecologic malignancy