Breast masses are three-dimensional space-occupying lesions in the breasts. This article provides an overview of the standard BI-RADS terminology used to describe breast masses in radiology reports and other reporting suggestions.
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Radiographic features
Breast masses are described differently by modality according to the BI-RADS lexicon 1-4. In all modalities, masses can be described by their size, location, and shape:
- size
- location of lesion
- laterality, i.e. left or right
- quadrant, i.e. upper/lower inner/outer, and/or clock face
- depth, i.e. anterior, middle, or posterior third
- distance from the nipple
- shape, which can be remembered by the mnemonic ROI:
- round
- oval
- irregular, i.e. neither round nor oval, which is usually suspicious for malignancy
Mammography
A mass must be seen on at least two different mammographic projections. It must demonstrate partially or completely convex-outward borders. When radiodense, the center of the lesion should be denser than the periphery. Possible additional descriptors include the following:
- margin, in order of increasing probability of malignancy, which can be remembered by the mnemonic COMIS:
- circumscribed, i.e. more than 75% of the circumference is well defined
- obscured, i.e. more than 25% of the circumference is hidden by adjacent or superimposed fibroglandular tissue
- microlobulated, i.e. small undulations, which is usually suspicious
- indistinct, i.e. none of the circumference is well defined, which is usually suspicious
- spiculated, i.e. with sharp linear radiations, which is usually suspicious
- density, in order of increasing probability of malignancy, of the lesion compared to equivalent volume fibroglandular tissue:
- fat-containing, which is almost always benign
- low density
- equal density
- high density
- associated features
- skin retraction
- nipple retraction
- skin thickening
- trabecular thickening
- axillary adenopathy
- architectural distortion
- calcifications
Ultrasound
A mass must be seen in two different planes during 2D ultrasound and in three planes during 3D ultrasound. Possible additional descriptors include the following:
- orientation, i.e. long axis of the lesion with respect to the skin
- parallel
- not parallel: e.g. taller than wide, vertical, round
- margin, which can be remembered by the mnemonic CAMIS:
- circumscribed, i.e. all of the circumference is well defined
- not circumscribed
- angular, i.e. some of the border forms a sharp corner
- microlobulated, i.e. small undulations
- indistinct, i.e. none of the circumference is well defined
- spiculated, i.e. with sharp linear radiations
- echo pattern
- anechoic, i.e. without internal echoes
- hypoechoic, i.e. low-level internal echoes lower than subcutaneous fat
- isoechoic, i.e. equal echogenicity compared to subcutaneous fat
- hyperechoic, i.e. more echogenicity than fat or equal to fibroglandular tissue
- heterogeneous, i.e. a mix of echogenicities within a solid mass
- complex cystic and solid, i.e. both anechoic and echogenic components
- posterior features
- no posterior features, i.e. no shadowing or enhancement deep to the mass
- enhancement
- shadowing
- combined pattern
- associated features
- calcifications in a mass
- architectural distortion
- vascularity
- absent
- internal vascularity
- vessels in rim
- elasticity assessment
- soft
- intermediate
- hard
- duct changes
- skin changes
- skin thickening
- skin retractions
- edema
MRI
A mass must demonstrate convex-outward margins. Possible additional descriptors include the following:
- margin
- circumscribed
- irregular
- spiculated
- internal enhancement characteristics
- homogeneous
- heterogeneous
- rim enhancement
- dark internal septations
- non-enhancing mass
- associated features
- nipple retraction
- nipple invasion
- skin retraction
- skin thickening
- skin invasion
- direct invasion
- inflammatory cancer
- axillary adenopathy
- pectoralis muscle invasion
- chest wall invasion
- architectural distortion
Differential diagnosis
Findings to consider other than mass:
- asymmetry on mammography, which is seen on only one view
- focal asymmetry on mammography, which is seen on at least two views but does not have convex borders
- focus on MRI, which has a diameter less than 5 mm
- non-mass enhancement on MRI, which has enhancement but does not meet the definition of a mass or focus
See also
- other imaging features of breast malignancy
- general types of masses