At the edges of curved masses, acoustic velocity changes and thin shadows are seen. This refractive edge shadowing is of no significance and should be distinguished from central shadowing, which is a property of the mass. Shadowing is associated with fibrosis, with or without an underlying carcinoma. Postsurgical scars, fibrous mastopathy, and cancers with a desmoplastic response will show posterior shadowing. Similar to a vertial (taller-than-wide) orientation, shadowing is a feature more helpful when present than when absent. Many cancers will exhibit enhancement or no change in posterior features, just as many cancers are wider-than-tall. However, fibrodenomas are not vertically oriented (taller-than-wide).