Is an asymmetry in the central breast at mid depth, better seen on the Craniocaudal (CC) view, less likely to be cancer?

Mammographic Asymmetry: Cancer Risk Assessment

An asymmetry in the central breast at mid depth, better seen on CC view, requires additional diagnostic evaluation with spot compression and ultrasound before determining cancer likelihood, but most asymmetries without associated suspicious features are benign. 1, 2

Immediate Next Steps

The finding described requires BI-RADS Category 0 assessment (incomplete, needs additional imaging evaluation), which mandates:

• Spot compression views to determine if the asymmetry persists or represents summation artifact 1, 2
• Magnification views if any associated microcalcifications are present 2
• Targeted ultrasound of the specific area to identify a potential mass or benign cause 2, 3

Cancer Risk Stratification

The malignancy risk depends critically on whether this represents a developing asymmetry (new or increased compared to prior) versus a stable asymmetry:

If This is a Developing Asymmetry (New or Increased):

• Cancer risk is 12.8% at screening and 42.9% when biopsy is recommended 4
• 23.8% of cancers presenting as developing asymmetry have no sonographic correlate, meaning negative ultrasound does not exclude malignancy 2, 4
• Biopsy is indicated even without ultrasound findings if the asymmetry is new, enlarging, or palpable 5, 4

If This is a Stable Asymmetry:

• Cancer risk approaches zero when asymmetric breast tissue is stable, contains no mass, no microcalcifications, and no architectural distortion 6
• In one study of 221 stable asymmetries followed for 36-42 months, zero cancers were found in non-palpable cases 6

Critical Pitfalls to Avoid

Do not rely on negative ultrasound alone. The most important pitfall is assuming a negative ultrasound excludes malignancy in a developing asymmetry. Nearly one-quarter of cancers presenting as developing asymmetry have no sonographic correlate 2, 4. The negative predictive value of ultrasound for focal asymmetric density is only 89.4%, meaning biopsy is still indicated when the asymmetry is new, enlarging, or palpable regardless of ultrasound findings 5.

Management Algorithm Based on Additional Imaging

If BI-RADS 1-3 After Complete Workup (Negative, Benign, or Probably Benign):

• Clinical re-examination in 3-6 months 1, 2
• Follow-up diagnostic mammogram and/or ultrasound every 6-12 months for 1-2 years to assess stability 1, 2
• Return to routine screening if stable 1, 2

If BI-RADS 4-5 After Complete Workup (Suspicious or Highly Suggestive):

• Tissue biopsy is mandatory using core needle biopsy (preferred) or needle localization excisional biopsy 1, 2
• Proceed even if ultrasound is negative 5, 4

Special Considerations

Low and intermediate-grade DCIS can present as asymmetry without calcifications, so absence of calcifications does not exclude malignancy 2. Additionally, digital breast tomosynthesis can improve sensitivity and specificity in evaluating asymmetries by reducing summation artifact 3.

Direct Answer to Your Question

Without knowing if this asymmetry is new or stable compared to prior mammograms, a definitive cancer likelihood cannot be stated. If this is a developing asymmetry, the cancer risk is substantial (12.8-42.9%) 4. If this is a stable asymmetry with no mass, calcifications, or architectural distortion, cancer is highly unlikely 6. The recommended spot compression and ultrasound will clarify this distinction and guide appropriate management 1, 2.