Breast mass

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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.

Radiographic features

Breast masses are described differently by modality according to the BI-RADS lexicon . 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
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