Benign and malignant characteristics of breast lesions at ultrasound

Benign and malignant characteristics of breast lesions at ultrasound allow the classification as either malignant, intermediate or benign based on work published by Stavros et al in 1995.

Radiographic features

Ultrasound

Malignant characteristics (with positive predictive values)

• sonographic spiculation: 87-90% ^1,4
  • alternate hypo-hyperechoic lines radiating perpendicularly from surface of nodules (if lesion is surrounded by echogenic tissue, hypoechoic strands will be seen; if lesion is surrounded by fat, echogenic strands may be seen)
• deeper (taller) than wide: 74-80% ^1,4
  • except in certain grade III Invasive ductal carcinomas
• microlobulations: 75%
  • small lobulations 1-2 mm on the surface; risk of malignancy rises with increasing numbers
• thick hyperechoic halo: 74%
• angular margins: 70%
• markedly hypoechoic nodule: 70%
• sonographic posterior acoustic shadowing: 50%
• branching pattern: 30%
  • multiple projections from the nodule within or around ducts extending away from the nipple, usually seen in larger tumours
• punctate calcifications: 25%
  • which usually do not shadow
• duct extension: 25%
  • is seen as projection from a nodule which extends radially within or around a duct towards the nipple
• heterogeneous echotexture ³ 
• compressibility
  • in general terms, benign lesions compress with transducer pressure and malignant lesions displace the breast tissue without changing in height; this is the basis for elastography

Benign characteristics (with negative predictive values)

• well circumscribed, hyperechoic tissue: ~100%
• wider than deep: 99%
• gently curving smooth lobulations (<3 in a wider than deep nodule, i.e. D/W ratio <1): 99%
• thin echogenic pseudocapsule in a wider than deep nodule: 99%
  • it is best seen on anterior/posterior margins, perpendicular to the beam
  • probably represents normal compressed tissue consistent with a non-infiltrative process

Treatment and prognosis

In all cases of lesions other than those which are absolutely benign, real time review by the radiologist is mandatory. Review of the mammogram is essential when interpretation of an ultrasound is performed. In patients under the age of 30 years, ultrasound is the primary imaging modality. In patients over the age of 40 years, both modalities are performed and interpreted in tandem. Any lesion classified as benign must be benign on both modalities.

Further workup strategy:

• if there is a single malignant feature: consider biopsy
• if there are no malignant features: then look for benign features
• if there are no malignant features or any benign features: indeterminate lesion, consider biopsy
• look at the mammogram