Breast imaging-reporting and data system (BI-RADS)

Last revised by Paulo Cesar Silva Lemos on 11 Oct 2023

BI-RADS (Breast Imaging-Reporting and Data System) is a risk assessment and quality assurance tool developed by American College of Radiology that provides a widely accepted lexicon and reporting schema for imaging of the breast. It applies to mammography, ultrasound, and MRI. This article reflects the 5th edition, published in 2013 1.

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Breast imaging studies are assigned one of seven assessment categories:

  • BI-RADS 0: incomplete

    • need additional imaging evaluation (additional mammographic views or ultrasound) and/or

    • for mammography, obtaining previous images not available at the time of reading

  • BI-RADS 1: negative

    • symmetrical and no masses, architectural distortion, or suspicious calcifications

  • BI-RADS 2: benign

    • 0% probability of malignancy

  • BI-RADS 3: probably benign

    • <2% probability of malignancy

    • short interval follow-up suggested

  • BI-RADS 4: suspicious for malignancy

    • 2-95% probability of malignancy

    • for mammography and ultrasound, these can be further divided:

      • BI-RADS 4A: low suspicion for malignancy (2-9%)

      • BI-RADS 4B: moderate suspicion for malignancy (10-49%)

      • BI-RADS 4C: high suspicion for malignancy (50-94%)

    • biopsy should be considered

  • BI-RADS 5: highly suggestive of malignancy

    • >95% probability of malignancy

    • appropriate action should be taken

  • BI-RADS 6: known biopsy-proven malignancy 

When there are multiple findings, the BI-RADS category for the exam is assigned the highest category in the following hierarchy, from lowest to highest: 1, 2, 3, 6, 0, 4, 5.

The vast majority of screening mammograms fall into BI-RADS 1 or 2 4. Screening mammograms with suspicious findings should generally be assigned BI-RADS 0 to indicate a callback for diagnostic evaluation, meaning additional views to confirm and further evaluate the finding.

BI-RADS provides standardized terminology to describe breast imaging findings.

These terms are only used in screening ultrasounds and not in the diagnostic setting.

  • homogeneous background echotexture - fat

  • homogeneous background echotexture - fibroglandular

  • heterogeneous background echotexture

See main article on breast echotexture.

  • shape

    • oval

    • round

    • irregular

  • orientation

    • parallel

    • not parallel

  • margin

    • circumscribed

    • angular

    • microlobulated

    • indistinct

    • spiculated

  • echo pattern (in comparison to subcutaneous fat)

    • anechoic

    • hyperechoic

    • hypoechoic

    • isoechoic

    • heterogeneous

    • complex cystic and solid

  • posterior features

    • no posterior features

    • enhancement

    • shadowing

    • combined pattern

See main article on breast masses.

  • calcifications in a mass

  • calcifications outside of a mass

  • intraductal calcifications

  • architectural distortion

  • duct changes

  • skin changes

    • skin thickening

    • skin retractions

  • edema

  • vascularity

    • absent

    • internal vascularity

    • vessels in rim

  • elasticity assessment

    • soft

    • intermediate

    • hard

  • fatty: the breasts are almost entirely fatty

  • scattered fibroglandular: there are scattered areas of fibroglandular density

  • heterogeneously dense: the breasts are heterogeneously dense, which may obscure small masses

  • extremely dense: the breasts are extremely dense, which lowers the sensitivity of mammography

See the main article on breast density.

  • shape

    • round

    • oval

    • irregular

  • margin

    • circumscribed

    • obscured

    • microlobulated

    • indistinct

    • spiculated

  • density

    • high density

    • equal density

    • low density

    • fat-containing

See main article on breast masses.

See main article on breast calcifications.

  • laterality

  • quadrant and clock face

  • depth

  • distance from the nipple

  • almost entirely fat

  • scattered fibroglandular tissue

  • heterogeneous fibroglandular tissue

  • extreme fibroglandular tissue

See the main article on breast density.

  • level

    • minimal

    • mild

    • moderate

    • marked

  • symmetry

    • symmetric

    • asymmetric

See main article on background parenchymal enhancement.

  • shape

    • round

    • oval

    • irregular

  • margins

    • circumscribed

    • irregular

    • spiculated

  • internal enhancement characteristics

    • homogeneous

    • heterogeneous

    • rim enhancement

    • dark internal septations

See main article on breast masses.

  • distribution

    • focal

    • linear

    • segmental

    • regional

    • multiple regions

    • diffuse

  • internal enhancement patterns

    • homogeneous

    • heterogeneous

    • clumped

    • clustered ring

See main article on non-mass enhancement.

  • nipple retraction

  • nipple invasion

  • skin retraction

  • skin thickening

  • skin invasion

    • direct invasion

    • inflammatory cancer

  • axillary adenopathy

  • pectoralis muscle invasion

  • chest wall invasion

  • architectural distortion

  • location

  • depth

  • initial phase

    • slow

    • medium

    • fast

  • delayed phase

    • persistent

    • plateau

    • washout

See main article on breast MRI enhancement curves.

Findings should be identified in the radiology report if they are suspicious, new, enlarging, or more extensive than at prior exams. Findings should be accompanied by a description of their location and an assessment of suspicion for malignancy.

When used appropriately, the BI-RADS assessment categories accurately reflect their positive predictive value for cancer, which are on average as follows for mammographically identified lesions that underwent biopsy 3:

  • BI-RADS 2: 0%

  • BI-RADS 3: 2%

  • BI-RADS 4: 30%

  • BI-RADS 5: 97%

There are other systems for classifying breast lesions:

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