What is the cutoff for endometrial thickness?

Endometrial Thickness Cutoffs

For postmenopausal women, the critical cutoff is ≤4 mm to exclude endometrial cancer with nearly 100% negative predictive value, while ≥5 mm warrants endometrial tissue sampling. 1

Postmenopausal Women

Asymptomatic Postmenopausal Women

• An endometrial thickness ≤4 mm conveys a negative predictive value for endometrial cancer of nearly 100%, eliminating the need for further evaluation 1
• When endometrial thickness is ≥5 mm, endometrial tissue sampling is generally recommended 1
• For asymptomatic women with endometrial thickness between 4-10 mm, consider additional risk factors (obesity, diabetes, hypertension, family history) when deciding whether to proceed with sampling 2
• An endometrial thickness >11 mm in asymptomatic postmenopausal women is a significant risk factor for endometrial hyperplasia or malignancy and mandates tissue sampling 3

Symptomatic Postmenopausal Women (with bleeding)

• Even a thickness >5 mm warrants investigation in women with postmenopausal bleeding 3
• The European Society for Medical Oncology uses a slightly more conservative cutoff of ≤3 mm for postmenopausal women, though the 4 mm threshold is more widely accepted 1

Premenopausal Women

• There is no validated absolute upper limit cutoff for endometrial thickness in premenopausal women 4
• Normal endometrial thickness varies throughout the menstrual cycle, making single measurements less clinically meaningful 4
• Endometrial thickness must be interpreted in the context of menstrual cycle phase 4

Critical Diagnostic Algorithm

Initial Assessment

• Transvaginal ultrasound (TVUS) combined with transabdominal ultrasound is the first-line screening test for measuring endometrial thickness 1
• Measure the double-layer endometrial thickness in the sagittal plane 1

Action Based on Thickness in Postmenopausal Women

If ≤4 mm:

• No further evaluation needed if asymptomatic 1
• Negative predictive value for cancer approaches 100% 1

If 5-10 mm:

• Endometrial tissue sampling recommended, especially if symptomatic 1
• Consider risk factors in asymptomatic women before proceeding 2

If >11 mm:

• Mandatory endometrial tissue sampling regardless of symptoms 3
• High risk for endometrial hyperplasia or malignancy 3

Sampling Techniques

• Pipelle or Vabra endometrial sampling devices have sensitivities of 99.6% and 97.1% respectively for detecting endometrial carcinoma 1
• If office-based sampling is inadequate or inconclusive, proceed to fractional curettage (95% diagnostic yield) or hysteroscopy with directed biopsy 3
• Hysteroscopy with directed biopsy is preferred over blind sampling for focal lesions 1

Important Caveats and Pitfalls

• Do not rely solely on endometrial thickness measurement without tissue sampling when thickness exceeds 11 mm 3
• Outpatient biopsy using Pipelle is only useful if positive; a negative result should not be considered definitive with significant endometrial thickening 3
• Abnormal echogenicity and texture of the endometrium correlate with significant underlying pathology even when thickness is normal 1, 4
• TVUS is sensitive for evaluating endometrial thickness but cannot reliably determine the etiology of endometrial thickening 1
• Consider sonohysterography to distinguish between focal and diffuse pathology when initial TVUS is inconclusive 3, 1
• Office endometrial biopsies have a false-negative rate of approximately 10% in postmenopausal women, necessitating further evaluation if clinical suspicion remains high 1