In a woman with a 6 × 4 mm vascularized endometrial lesion and an endometrial thickness of 7.6 mm but no abnormal uterine bleeding, what is the probability that the lesion is malignant?

Risk of Malignancy in Asymptomatic Women with Vascularized Endometrial Lesion

In an asymptomatic woman with a 6 × 4 mm vascularized endometrial lesion and endometrial thickness of 7.6 mm, the risk of malignancy is approximately 3.7-6.7%, warranting tissue diagnosis through hysteroscopy with directed biopsy rather than blind endometrial sampling. 1, 2

Risk Stratification Based on Endometrial Thickness

The probability of malignancy in your patient depends critically on menopausal status and the specific characteristics of the lesion:

In Postmenopausal Women (Most Relevant Context)

• At 7.6 mm endometrial thickness in asymptomatic postmenopausal women, the overall malignancy risk is approximately 3.7% 1
• When endometrial thickness reaches 8 mm or above (your patient is close at 7.6 mm), the optimal discrimination threshold shows malignancy risk increases substantially, with an area under the curve of 0.755 2
• The risk escalates to 16.3% when endometrial thickness reaches ≥10 mm in asymptomatic postmenopausal women 1
• In one prospective study of 304 asymptomatic postmenopausal women with thickened endometrium (mean 12 mm), only 3.9% had endometrial adenocarcinoma on hysteroscopy and histology 3

Critical Distinction: Focal Lesion vs. Diffuse Thickening

Your patient has a focal vascularized lesion, which changes the clinical picture significantly:

• The presence of vascularity within an endometrial lesion can indicate either endometrial polyps or cancer, though current evidence shows Doppler cannot definitively differentiate between benign and malignant endometrial lesions 4
• In a retrospective cohort of 154 asymptomatic postmenopausal women with thickened endometrium, 93 had polyps (60%), and among those who underwent polypectomy, only 1.4% had cancer and 1.4% had complex hyperplasia with atypia 5
• The commonest pathology in asymptomatic women with thickened endometrium is endometrial polyps (74.3%), not malignancy 3

Why Blind Endometrial Sampling Is Inadequate

Blind endometrial sampling techniques (Pipelle, Vabra) have a 10% false-negative rate and may miss focal lesions entirely, despite their 99.6% and 97.1% sensitivity for diffuse endometrial carcinoma 1, 6

In the study of asymptomatic women with polyps, two cases of malignancy had office endometrial biopsies showing "insufficient endometrium" and "inactive endometrium" respectively—both were false negatives that only became apparent after hysteroscopic polypectomy 5

Recommended Diagnostic Algorithm

Step 1: Hysteroscopy with Directed Biopsy

Hysteroscopy with visually-directed biopsy is mandatory for focal endometrial lesions, as it allows direct visualization and targeted sampling of the vascularized lesion 1, 2

Step 2: Risk Factor Assessment

While awaiting hysteroscopy, consider additional risk factors that increase malignancy probability:

• Diabetes, hypertension, elevated BMI, and blood flow signals on Doppler collectively increase the predictive value for malignancy (AUC 0.834 when combined with endometrial thickness) 2
• Age significantly impacts risk: at the same endometrial thickness, cancer risk increases from 4.1% at age 50 to 9.3% at age 79 7

Step 3: If Hysteroscopy Shows Polyp

Even if the lesion appears benign on hysteroscopy, polypectomy should be performed in asymptomatic women when endometrial thickness is ≥8 mm or when the polyp demonstrates vascularity, as malignancy can be present despite benign hysteroscopic appearance 2, 5

Common Pitfalls to Avoid

Do not rely on office endometrial biopsy alone for focal lesions—the false-negative rate is unacceptably high 1, 5

Do not assume that absence of bleeding means low cancer risk—10-20% of endometrial cancers occur in asymptomatic women 3, 8

Do not use the 4 mm threshold for asymptomatic women—this threshold applies only to symptomatic postmenopausal women with bleeding and has a different risk profile 1, 8

Do not delay evaluation based on the small size (6 × 4 mm) of the lesion—malignancy has been documented in focal lesions regardless of size when other risk factors are present 5

Bottom Line

Your patient's 3.7-6.7% malignancy risk, combined with the focal vascularized nature of the lesion, mandates hysteroscopy with directed biopsy rather than observation or blind sampling. 1, 2 The most likely diagnosis remains benign endometrial polyp (60-74% probability), but the only way to definitively exclude the 3.7-6.7% cancer risk is through direct visualization and targeted tissue sampling. 3, 5