Benign and malignant characteristics of breast lesions at ultrasound

Breast lesions at ultrasound have a number of characteristics which allows the classification as either malignant, intermediate or benign. In 1995, A. Thomas Stavros published an important paper in Radiology ¹ which established the usefulness of various ultrasound features in distinguishing benign from malignant lesions.

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, you will see hypoechoic strands. 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 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
• shadowing ³ :
• 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 markedly 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. It probably represents normal compressed tissue consistent with a non infiltrative process.

Further work up 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 >> reconsider biopsy 
• look at the mammogram.

Practical considerations

In all cases of lesions other than absolutely benign, real time review by the radiologist is mandatory. This is the single biggest source of ultrasound misinterpretation in everyday practice (see case 21508).

Review of the mammogram is essential when interpretation of an ultrasound is done. In those under 30 years, ultrasound is the primary imaging modailty. In those over 40, both modalities are performed and interpretted in tandem.

Any lesion classified as benign must be benign on both modalities.

See also

• ultrasound evaluation of breast cysts
• breast ultrasound