What percentage of endometrial polyps convert to cancer?

Malignant Transformation Rate of Endometrial Polyps

The overall risk of malignancy in endometrial polyps ranges from 0.3% to 4.8%, with most large studies reporting rates between 1.3% and 1.8%. 1, 2, 3

Overall Malignancy Rates

The baseline risk of cancer in endometrial polyps is relatively low across all populations:

• 1.3% overall cancer rate in a large cohort of 1,011 women with endometrial polyps 2
• 1.54% malignancy rate in a retrospective analysis of 1,027 cases 3
• 4.75% malignancy rate (including atypical hyperplasia) in menopausal women specifically 1
• Only 0.3% of cancers were confined to the polyp itself, with most malignancies arising in adjacent endometrium 2

Risk Stratification by Clinical Factors

High-Risk Group (12.3% malignancy risk):

Postmenopausal women over age 59 with abnormal uterine bleeding have a dramatically elevated risk of 12.3% 1. This subgroup requires mandatory hysteroscopic resection 1.

Intermediate-Risk Groups (3-4% malignancy risk):

Postmenopausal women with bleeding (any age):

• 3.8% risk of cancer or atypical hyperplasia 2
• Abnormal uterine bleeding in postmenopause increases risk 31-fold (OR: 31.1,95% CI [10.3,111]) 3

Postmenopausal status alone:

• 3-fold increased risk (OR: 3.05,95% CI [1.54,6.19]) compared to premenopausal women 3
• 1.9% risk even without bleeding 2

Low-Risk Groups (≈1% malignancy risk):

Premenopausal women:

• 0.9% risk without bleeding 2
• 1.0% risk with bleeding 2

All other postmenopausal subgroups not meeting high-risk criteria:

• 2.31-3.78% risk range 1

Independent Predictors of Malignancy

On multivariate analysis, the strongest independent predictors are:

• Age: Each year increases risk (OR: 1.06-1.08 per year) 1, 4
• Abnormal uterine bleeding: 3.5-fold increased risk (OR: 3.53,95% CI [1.87-6.65]) 4
• Family history of gynecological cancer: Nearly 3-fold increased risk (OR: 2.88,95% CI [1.08-7.67]) 1

Important caveat: Endometrial thickness does not correlate with malignancy risk in polyps on either univariate or multivariate analysis 1. This differs from diffuse endometrial pathology.

Hysteroscopic Features Predicting Malignancy

When visualized directly, certain hysteroscopic findings dramatically increase cancer likelihood:

• Ulcerative changes: 100% specificity and positive predictive value for malignancy 5
• Hyper-vascularity: 143-fold increased odds (OR: 142.6,95% CI [25.98-783.4]) 5
• Irregular surface: 12-fold increased odds (OR: 12.02,95% CI [1.765-81.83]) 5

In contrast, pedunculated small growths with smooth surfaces are typically benign (seen in 38.3% of benign polyps) 5.

Clinical Management Algorithm

For postmenopausal women >59 years with abnormal bleeding:

• Proceed directly to hysteroscopic resection (12.3% malignancy risk) 1

For postmenopausal women with bleeding (any age):

• Hysteroscopic resection recommended (3.8% malignancy risk) 2, 3

For asymptomatic postmenopausal women or premenopausal women with bleeding:

• Individual risk assessment considering age, family history, and BMI 1, 4
• Risk ranges 1-3%, but not insignificant 1, 2
• Hysteroscopy with targeted biopsy preferred over blind sampling for polyps 6

For premenopausal asymptomatic women:

• Lowest risk group (0.9%) 2
• Expectant management may be reasonable after informed discussion 1

Critical Pitfalls

Blind endometrial sampling is unreliable for polyps because it may miss focal lesions entirely 6. When polyps are visualized on imaging, hysteroscopy with directed biopsy is mandatory to exclude malignancy 6.

The presence of premalignant lesions (atypical hyperplasia) adds another 0.5-2.67% to the overall risk, bringing total concerning pathology to approximately 3-7% depending on the population studied 2, 3.