Should a screening mammogram showing asymmetry be followed up with a diagnostic mammogram?

Management of Screening Mammogram Showing Asymmetry

Yes, a screening mammogram showing asymmetry should be followed up with diagnostic mammography that includes additional views (spot compression and magnification views) to characterize the finding, followed by targeted ultrasound of the area of concern. 1

Diagnostic Workup Algorithm

Initial Diagnostic Imaging

• Diagnostic mammography with additional views is the foundation of evaluation and should include spot compression views to determine if the asymmetry persists or represents summation artifact from overlapping normal breast tissue. 2, 1

• Magnification views are particularly helpful if any associated microcalcifications are present with the asymmetry. 1

• Targeted ultrasound should be performed concurrently with diagnostic mammography to identify potentially benign causes of the asymmetry and to identify a target for biopsy if indicated. 1, 3

Management Based on BI-RADS Assessment

For BI-RADS 1-3 (Negative, Benign, or Probably Benign):

• Clinical re-examination in 3-6 months with imaging as needed. 2, 1
• Follow-up diagnostic mammogram and/or ultrasound every 6-12 months for 1-2 years to assess stability. 2, 1
• If stable, return to routine screening. 2, 1
• If findings progress on physical exam or imaging, proceed to biopsy. 2

For BI-RADS 4-5 (Suspicious or Highly Suggestive of Malignancy):

• Tissue biopsy is recommended, preferably using core needle biopsy. 2, 1

Critical Clinical Considerations

Importance of Complete Workup Despite Negative Ultrasound

• The absence of an ultrasound correlate does not exclude malignancy and should not preclude biopsy of a suspicious asymmetry. 3, 4

• In developing asymmetries (new or increased compared to prior), 23.8% of cancers had no sonographic correlate, highlighting the critical importance of mammographic evaluation. 1, 4

Risk Stratification

• Developing asymmetry carries the highest suspicion for malignancy among asymmetry types, with a positive predictive value of 12.8% at screening and 42.9% when biopsy is recommended. 1, 4

• Both ductal carcinoma in situ (DCIS) and invasive carcinomas can manifest as asymmetries, and low and intermediate-grade DCIS can present as an asymmetry without calcifications. 1

Common Pitfalls to Avoid

• Do not dismiss an asymmetry based solely on negative ultrasound findings, as nearly one-quarter of cancers presenting as developing asymmetry have no ultrasound correlate. 4

• Do not assume all asymmetries are summation artifacts without performing spot compression views to confirm the finding disappears. 1

• Age and breast density matter: For asymmetries detected on screening, age ≥55 years and lower breast density are independent predictors of malignancy. 5