Which discrete structures of the breast are recognized on ultrasonography?

Updated: Jan 24, 2017
  • Author: Durre Sabih, MBBS, MSc, FRCP(Edin); Chief Editor: Mahan Mathur, MD  more...
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Ultrasound shows certain discrete structures that can be recognized. From superficial to deep these are as follows:

  • Skin: This is recognized as a thin hyperechoic to isoechoic zone between 2 thinner hyperechoic lines. Usually this is less than or equal to 2 mm in thickness but is slightly thicker over the areolae.

  • Subcutaneous fat (premammary fat): This is the reference tissue. Premammary fat is more hypoechoic than fat elsewhere and has a lobular structure with the fat lobules surrounded by a very thin echogenic layer.

  • Parenchyma: This layer appears as an echogenic plate; this can be homogenous in some women but can be heterogeneous, almost tigroid in appearance in others, especially in young women. This can also vary in echogenicity from echogenic in usual cases to almost isoechoic in lactating breasts. Within the parenchyma ducts, the terminal ductal lobular unit (TDLU) can be seen occasionally.

The ducts can be seen as thin echogenic lines representing collapsed and apposed duct walls, or lines surrounded by a hypoechoic zone that is the loose stromal tissue surrounding the ducts. Frequently, only the isoechoic periductal stromal tissue is seen, giving the almost striped (tigroid) appearance. With progressive accumulation of intraductal fluid, the ducts can appear as tubes that can be up to 5 mm across. Duct ectasia becomes more frequent with age, and almost 50% women have ectatic ducts by the age of 50 years. Duct ectasia is mostly an incidental finding but may be associated with discharge and periductal mastitis.

With very high-resolution images, TDLUs are sometimes seen as small hypoechoic elongated or rounded structures. These are usually located peripherally in the parenchymal plate, more numerous in the anterior part than the posterior part. [12]

Cooper ligaments attach to the parenchymal surface from the anterior mammary fascia and can be seen as thin echogenic bands, widening as these insert into the anterior parenchymal surface. A few Cooper ligaments are seen posteriorly as well.

For more information about the relevant anatomy, see Breast Anatomy.

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