Is breast asymmetry in a 55-year-old woman, identified on a craniocaudal (CC) view, likely to be cancer?

Breast Asymmetry Cancer Risk Assessment

Breast asymmetry seen only on CC view in an asymptomatic 55-year-old woman requires additional diagnostic imaging with spot compression and ultrasound before determining cancer likelihood, but the probability of malignancy is relatively low (less than 15%) if this represents a simple asymmetry rather than a developing asymmetry. 1, 2

Immediate Next Steps

The finding described requires completion of diagnostic workup before cancer risk can be accurately determined:

• Perform spot compression views to determine if the asymmetry persists or represents summation artifact from overlapping normal breast tissue 1, 3
• Obtain magnification views to evaluate for any associated microcalcifications that may not be visible on standard views 1
• Conduct targeted ultrasound of the area to identify a correlating mass or architectural distortion that would increase suspicion for malignancy 1, 2

Risk Stratification Based on Asymmetry Type

The cancer risk depends critically on whether this is a simple asymmetry versus a developing asymmetry:

Simple Asymmetry (Stable or First Detection)

• If the asymmetry disappears on spot compression views, it represents summation artifact and is benign 3
• If persistent but stable compared to prior mammograms (if available), without associated mass, calcifications, or architectural distortion, the cancer risk is very low 4
• A prospective study of 221 cases of asymmetric breast tissue found zero cancers in patients without palpable abnormalities 4

Developing Asymmetry (New or Increasing)

• If this asymmetry is new or increased compared to prior studies, the positive predictive value for cancer is 12.8% at screening and 42.9% when biopsy is recommended 2, 5
• Developing asymmetry is an uncommon but significant manifestation of breast cancer and should be viewed with heightened suspicion 2
• Notably, 23.8% of cancers presenting as developing asymmetry have no ultrasound correlate, so absence of sonographic findings does not exclude malignancy 1

BI-RADS Classification and Management

After completing spot compression and ultrasound:

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

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

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

• Tissue biopsy is mandatory, preferably core needle biopsy 6, 1
• Biopsy is indicated if the asymmetry is associated with suspicious microcalcifications, architectural distortion, or represents a new/increasing finding 1

Critical Pitfalls to Avoid

• Do not dismiss asymmetry without completing the diagnostic workup with spot compression and ultrasound, as recommended by NCCN guidelines 6, 1
• Do not assume benignity based solely on negative ultrasound, particularly if mammographic features are suspicious, since nearly one-quarter of cancers presenting as developing asymmetry lack sonographic correlation 1
• Low and intermediate-grade DCIS can present as asymmetry without calcifications, so absence of calcifications does not exclude malignancy 1
• Failure to biopsy developing asymmetries may lead to delayed diagnosis of breast cancer 5

Clinical Context for This Patient

At age 55, this patient is in a higher-risk age group for breast cancer. The fact that she is asymptomatic is reassuring but does not eliminate cancer risk. The key determinant of cancer likelihood is whether prior mammograms are available for comparison—if this asymmetry is new or increasing, the cancer risk increases substantially from very low to approximately 13-43% depending on final imaging assessment 2, 5.