Understanding Mammographic Asymmetry on CC View
What the Radiologist Means by "Asymmetry"
The radiologist identified an area of increased breast tissue density on the craniocaudal (CC) view of your right breast compared to the corresponding area in the left breast, which requires additional imaging to determine if this represents overlapping normal tissue (summation artifact) or a true lesion. 1, 2
Most asymmetries (approximately 97.7%) are benign or caused by normal breast tissue overlapping during mammography, but asymmetry can indicate breast cancer, including ductal carcinoma in situ (DCIS) or invasive cancer. 2, 3, 4
Required Next Steps for BI-RADS Category 0
You need diagnostic mammography with additional specialized views plus targeted ultrasound of the right breast area of concern. 1, 2
Specific Diagnostic Imaging Protocol:
Spot compression views: These determine whether the asymmetry persists (indicating a real finding) or disappears (indicating summation artifact from overlapping normal tissue). 1, 2
Magnification views: These evaluate for any associated microcalcifications that might indicate malignancy. 1, 2
Rolled views: The breast is repositioned medially or laterally while keeping the X-ray beam angle the same, which separates overlapping structures and directly shows summation artifacts in 74.6% of cases. 4, 5
Targeted ultrasound: This must be performed concurrently to identify potentially benign causes (like cysts or lymph nodes) or identify a target for biopsy if needed. 1, 2
What Happens After Additional Imaging
If BI-RADS 1-3 (Negative, Benign, or Probably Benign):
- Clinical re-examination in 3-6 months 1
- Follow-up imaging (diagnostic mammogram and/or ultrasound) every 6-12 months for 1-2 years to confirm stability 6, 1
- Return to routine screening if stable 1
If BI-RADS 4-5 (Suspicious or Highly Suggestive of Malignancy):
- Tissue biopsy is mandatory using core needle biopsy (preferred method) or needle localization excisional biopsy. 6, 1, 2
Critical Points to Understand
Do not be falsely reassured if ultrasound shows nothing abnormal—biopsy may still be needed if the mammographic asymmetry appears suspicious. Developing asymmetries have a 12.8% cancer rate at screening and 42.9% when biopsy is recommended, and 23.8% of cancers presenting as asymmetry have no ultrasound correlate. 1
Mammography alone has limited sensitivity (15%-68%) for detecting malignancy, which is why the multimodality approach with ultrasound is essential. 2
Low and intermediate-grade DCIS can present as asymmetry without calcifications, so absence of calcifications does not exclude malignancy. 1