What endometrial thickness is concerning?

Concerning Endometrial Thickness

In postmenopausal women, an endometrial thickness ≥5 mm is concerning and warrants endometrial tissue sampling, while in asymptomatic postmenopausal women, a threshold of >11 mm should prompt biopsy. 1, 2

Postmenopausal Women with Bleeding

• An endometrial thickness ≤4 mm has a negative predictive value for endometrial cancer of nearly 100%, making further evaluation unnecessary in this group 1
• When endometrial thickness measures ≥5 mm, endometrial tissue sampling is recommended due to the significantly elevated cancer risk (approximately 7.3%) 1, 3
• The American College of Radiology endorses the 4 mm threshold as the upper limit of normal, though some European guidelines use a more conservative 3 mm cutoff 1

Important Caveat for Afro-Caribbean Populations

• In Afro-Caribbean women, the standard 5 mm threshold may be unreliable, as one study found that 50% of endometrial cancer cases had endometrial thickness between 3-4 mm 4
• This suggests that ethnic background should influence the decision to pursue tissue sampling, with a lower threshold potentially warranted in this population 4

Asymptomatic Postmenopausal Women

• An endometrial thickness >11 mm in asymptomatic postmenopausal women carries a cancer risk of approximately 6.7%, justifying endometrial biopsy 2, 3
• Endometrial thickness ≤11 mm in asymptomatic women has an extremely low cancer risk (0.002%), making biopsy unnecessary 3
• For measurements between 4-11 mm, decisions should be individualized based on additional risk factors including age >65 years, time since menopause >5 years, and other endometrial cancer risk factors 2, 5

Age-Related Risk Stratification

• Cancer risk increases substantially with age even at the same endometrial thickness: at 11 mm threshold, risk rises from 4.1% at age 50 to 9.3% at age 79 3
• This supports more aggressive evaluation in older postmenopausal women even with borderline measurements 3

Diagnostic Algorithm

Initial Assessment

• Transvaginal ultrasound (TVUS) combined with transabdominal ultrasound is the recommended first-line imaging for complete pelvic assessment 1
• Measure endometrial thickness as the first step in the diagnostic pathway 1

Follow-up Based on Thickness

For symptomatic postmenopausal women:

• ≤4 mm: No further evaluation needed 1
• ≥5 mm: Proceed to endometrial sampling 1

For asymptomatic postmenopausal women:

• ≤11 mm: No biopsy needed unless additional risk factors present 2, 3

• 11 mm: Endometrial biopsy recommended 2, 3

• 4-11 mm with risk factors: Consider biopsy on case-by-case basis 2, 5

Tissue Sampling Methods

• Pipelle or Vabra endometrial sampling devices have sensitivities of 99.6% and 97.1% respectively for detecting endometrial carcinoma 1
• For focal lesions, hysteroscopy with directed biopsy is preferred over blind sampling 1
• If office-based sampling is inadequate, proceed to fractional curettage (diagnostic in 95% of cases) 2

Critical Pitfalls to Avoid

• Do not rely on TVUS alone to determine etiology of thickening—ultrasound is sensitive for detecting thickness but cannot reliably characterize the pathology 1
• Abnormal echogenicity and texture may indicate pathology even with normal thickness, requiring clinical correlation 1
• Intracavity fluid can falsely elevate endometrial thickness measurements, potentially leading to unnecessary procedures 6
• Blind endometrial sampling may miss focal lesions—use sonohysterography or hysteroscopy when focal abnormalities are suspected 1, 2
• A negative outpatient Pipelle biopsy should not be considered definitive when endometrial thickness significantly exceeds thresholds 2

Adjunctive Imaging

• Sonohysterography can distinguish focal from diffuse pathology when initial TVUS shows abnormalities, with sensitivity of 96-100% 2
• Color and spectral Doppler evaluation of internal vascularity can help identify abnormal vascular patterns suggestive of malignancy 2