What are the next steps for a patient with asymmetry on the CC view of the right breast and no mammographic evidence of malignancy in the left breast, classified as BI-RADS (Breast Imaging-Reporting and Data System) Category 0?

Management of BI-RADS Category 0: Right Breast Asymmetry on CC View

The patient requires immediate diagnostic mammography with additional views (spot compression, magnification, or other specialized views) of the right breast, typically with adjunctive targeted ultrasound, to complete the evaluation and assign a final BI-RADS category. 1

Understanding BI-RADS Category 0

BI-RADS Category 0 represents an incomplete assessment that requires additional imaging evaluation before a final determination can be made 1. This category is almost exclusively used in screening situations when a finding cannot be fully characterized with standard two-view mammography alone 1, 2.

• Category 0 is not a final assessment - it indicates the radiologic evaluation is incomplete and additional workup is mandatory before determining the appropriate management pathway 1, 2
• The asymmetry on CC view requires further characterization to determine if it represents summation artifact, normal fibroglandular tissue, or a true lesion requiring biopsy 3, 4

Immediate Next Steps

Diagnostic Mammography

Perform diagnostic mammography with specialized views of the right breast: 1

• Spot compression views to evaluate the margins and determine if the asymmetry persists or resolves (suggesting summation artifact) 5, 3
• Magnification views if microcalcifications are present or suspected 1, 5
• Lateral or rolled views to localize the finding in three-dimensional space 3
• Digital breast tomosynthesis may replace or supplement traditional diagnostic views to improve sensitivity and specificity 1, 3

Adjunctive Ultrasound

Targeted ultrasound of the right breast should be performed, particularly for asymmetries: 1

• Ultrasound is frequently performed for masses or asymmetries to identify a correlate and characterize the finding 1
• The overall final BI-RADS assessment represents the cumulative findings of both mammography and ultrasound - the category may increase, decrease, or remain the same after ultrasound evaluation 1, 2
• Lack of an ultrasound correlate does not preclude the need for biopsy if the mammographic finding remains suspicious 3

Subsequent Management Based on Final BI-RADS Category

After completing diagnostic imaging, management depends on the final combined assessment:

BI-RADS 1-2 (Negative or Benign)

• Resume routine annual screening mammography 1, 2
• The asymmetry was likely summation artifact or normal tissue 4

BI-RADS 3 (Probably Benign)

• Diagnostic mammography at 6 months, then every 6-12 months for 1-2 years 1, 2
• If stable or resolved, resume routine screening 1, 2
• If the lesion increases in size or changes characteristics, proceed to biopsy 1
• Exception: Consider initial biopsy if follow-up is uncertain, patient strongly desires biopsy, or strong family history of breast cancer 1

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

• Tissue diagnosis is mandatory using core needle biopsy (preferred) or needle localization excisional biopsy 1, 2
• Pathology-imaging concordance must be confirmed 1
• If pathology and imaging are discordant, repeat imaging and/or additional tissue sampling or surgical excision is required 1

Critical Considerations for Asymmetries

Developing asymmetries warrant particular attention: 3, 6

• A developing asymmetry (new or increased compared to prior) is an uncommon but important manifestation of breast cancer and should be viewed with suspicion 3
• Even if the asymmetry appears similar to fibroglandular tissue, complete diagnostic evaluation is essential 3, 4
• The most worrisome finding determines the overall BI-RADS category when multiple abnormalities are present 1, 2

Common Pitfalls to Avoid

• Never resume routine screening without completing the diagnostic workup - Category 0 mandates additional evaluation 1, 2
• Do not assume the asymmetry is benign without diagnostic imaging - asymmetry may be the only manifestation of breast cancer on standard views 6
• Obtain prior mammograms for comparison when available - this is particularly important for low-suspicion lesions and helps determine if the asymmetry is new or stable 1
• Do not delay biopsy if the final assessment is BI-RADS 4 or 5, even if ultrasound is negative 3