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BI-RADS: Standardizing Breast Imaging and Reporting


BI-RADS: Breast Imaging Reporting and Data System, was developed by the American College of Radiology (ACR) to standardize mammogram reporting, as well as breast ultrasound and MRI reporting.

The standard mammogram report includes the following

  • Indication and type of mammogram (screening/diagnostic)
  • Statement regarding breast density
  • Description of pertinent findings including size and location, oriented by quadrant and clock position
  • Summary of important findings and BI-RADS category


BI-RADS Classification Standardizes Findings and Recommendations for Further Management

BI-RADS 0 : Incomplete

  • Recall for additional imaging/comparison with prior examinations, or both

BI-RADS 1: Negative  (Essentially 0% chance of malignancy)

  • Routine screening

BI-RADS 2: Benign (Essentially 0% likelihood of malignancy)

  • Routine screening

BI-RADS 3: Probably benign (> 0% but ≤ 2% likelihood of malignancy)

  • 6 month follow-up or continued surveillance

BI-RADS 4: Suspicious (> 2% but < 95% likelihood of malignancy)

  • 4A: Low suspicion for malignancy (> 2% to ≤ 10% likelihood)
  • 4B: Moderate suspicion for malignancy (> 10% to ≤ 50% likelihood)
  • 4C: High suspicion for malignancy (> 50% to < 95% likelihood)
  • Tissue diagnosis needed for all BI-RADS 4  categories

BI-RADS 5: Highly suggestive of malignancy (95% likelihood of malignancy)

  • Tissue diagnosis needed

BI-RADS 6: Known, biopsy proven malignancy

  • Surgical excision when appropriate

Density Categories

  • Category a: Breasts are almost entirely fatty
    • Prevalence: 10% of the population
    • Mammography considered highly sensitive in this setting (88%)
  • Category b: There are scattered areas of fibroglandular density
    • Prevalence: 43% of the population
    • Still sensitive but decreased from category a (82%)
  • Category c: Breasts are heterogeneously dense
  • Category d: Breasts are extremely dense
    • Significantly lowers sensitivity of mammography (62%)
    • Note: Breast cancer risk is 2.1 relative risk compared to average breast density

Learn More – Primary Sources:

ACOG Practice Bulletin No 164. Diagnosis and Management of Benign Breast Disorders 

ACR BI-RADS® Atlas, Breast Imaging Reporting and Data System

ACOG Committee Opinion 625: Management of with Dense Breasts Diagnosed with Mammography