Transverse ultrasound image of the breast shows an irregularly shaped hypoechoic mass (between calipers) with posterior attenuation of the acoustic transmission ("shadowing"). The shadowing obscures the posterior margin of the mass.
- Attenuation characteristics of a mass with respect to its acoustic transmission
- Four patterns: no posterior acoustic features, enhancement, shadowing and combined
- Attenuation of sound beam deeper to a mass
- Associated with fibrosis, with or without underlying carcinoma
- DDx: scars, fibrous mastopathy and cancer with desmoplastic response
- Helpful feature when present (suggesting above diagnoses)
- Should be distinguished from "refraction or edge shadowing" which is a thin shadow seen at the edges of curved masses that is of no significance