What to do if a mammogram shows dense breast tissue?

Management of Dense Breast Tissue on Mammogram

Women with dense breasts (heterogeneously or extremely dense) should be informed about their breast density and counseled about supplemental screening options, with breast MRI or abbreviated MRI being the most effective supplemental modality for cancer detection, particularly for those with extremely dense breasts. 1

Understanding Dense Breasts and Their Clinical Significance

Dense breast tissue affects approximately half of women undergoing screening mammography and presents two critical challenges 1:

• Reduced mammographic sensitivity: Sensitivity can decrease to as low as 30% in women with dense breasts, compared to 70-85% overall 1, 2
• Independent cancer risk factor: Women with extremely dense breast tissue have a 4-6 fold greater risk of developing breast cancer compared to those with fatty tissue 1, 2
• Higher interval cancer rates: Women with dense breasts experience increased rates of interval cancers (cancers detected between screening rounds), which often have worse prognosis 1

Required Patient Notification

As of September 2024, FDA regulations mandate that all mammography facilities notify patients of their breast density status 1. Patients must be informed that:

• Dense breast tissue can make it harder to evaluate mammogram results 1
• Dense breast tissue is associated with increased breast cancer risk 1
• Supplemental imaging studies may be beneficial to aid in cancer detection 1

Recommended Supplemental Screening Approach

First-Line Supplemental Screening Options

For women with extremely dense breasts, the evidence strongly supports supplemental MRI screening 1, 3:

• Breast MRI with contrast demonstrates sensitivity ranging from 81-100% and is the most effective supplemental modality 4
• Abbreviated breast MRI (AB-MRI) shows cancer detection rates of 15.2 per 1,000 examinations compared to 6.2 per 1,000 with digital breast tomosynthesis in dense breasts 5
• Interval cancer reduction: Supplemental MRI reduced interval cancers from 5.0 per 1,000 to 2.5 per 1,000 screenings in women with extremely dense breasts 3
• Cancers detected by MRI tend to be smaller, lymph node negative, and less biologically aggressive 1, 5

Alternative Supplemental Options

Digital Breast Tomosynthesis (DBT) 1, 5:

• Increases cancer detection rates in both dense and non-dense tissue 1
• Reduces recall rates by 15-63% compared to standard mammography 1
• More accessible and less expensive than MRI 5

Whole Breast Ultrasound 1, 5:

• Increased cancer detection from 7.6 to 11.8 cancers per 1,000 women screened when added to mammography 1
• Higher false-positive rates and lower positive predictive values for biopsies 5
• May be appropriate for women who cannot access or tolerate MRI 6

Contrast-Enhanced Mammography (CEM) 1:

• Utilizes functional imaging to identify malignancy 1
• Promising results but requires further validation 4

Risk Stratification Approach

The choice of supplemental screening should be guided by individual breast cancer risk assessment 1:

• Risk assessment should be performed for all women by age 25, especially Black women and those of Ashkenazi Jewish descent 1, 5
• Average lifetime risk (<15%): Consider DBT or whole breast ultrasound 1
• Intermediate risk (15-20%): Consider whole breast ultrasound or abbreviated MRI 1
• High risk (>20%): Breast MRI with contrast is most appropriate 1

Important Caveats and Limitations

Evidence Limitations

The U.S. Preventive Services Task Force notes that current evidence is insufficient to recommend a specific screening strategy for women with dense breasts, as data do not yet demonstrate that supplemental screening reduces breast cancer mortality or improves quality of life 1. However, this reflects the lag time needed to demonstrate mortality benefit, not lack of cancer detection.

Practical Considerations

• False-positive rates: All supplemental screening modalities increase false-positive results, recalls, and biopsies 1
• MRI limitations: High cost, longer scan times, requires contrast administration, and limited availability 4
• Breast density variability: Many women move between "dense" and "nondense" classifications on sequential mammograms 1
• Overdiagnosis potential: Some detected cancers may represent overdiagnosis, though existing data cannot estimate this proportion 1

Clinical Decision-Making Algorithm

1. Confirm breast density category from mammography report (heterogeneously or extremely dense) 1
2. Perform breast cancer risk assessment by age 25 1, 5
3. For extremely dense breasts with any risk level: Discuss supplemental MRI or abbreviated MRI as first-line option 1, 5, 3
4. For heterogeneously dense breasts: Tailor supplemental screening based on risk stratification and patient preferences 1
5. If MRI unavailable or contraindicated: Consider DBT or whole breast ultrasound as alternatives 5, 6
6. Discuss trade-offs: Inform patients about increased cancer detection versus higher false-positive rates 1

The most recent and highest quality evidence supports supplemental MRI screening for women with extremely dense breasts, demonstrating significant reduction in interval cancers and superior cancer detection rates compared to other modalities. 3