Occult breast masses: use of a mammographic localizing grid for US evaluation.

To determine if there was a problem of misidentification of mammographically detected masses with freehand ultrasound (US), the authors examined 50 mammographically distinct masses in 47 patients who were scheduled to undergo needle localization. In only six cases were the masses to be localized in an area of the breast that contained other mammographic opacities that could have led to problems of identification. The patients were first studied with freehand US. Results were then compared with those subsequently obtained with a fenestrated mammographic compression grid to guide the US evaluation. Needle localization was then performed. In five of 50 cases, masses detected with freehand US and initially believed to correspond to the mammographically detected mass were subsequently found to represent different areas of the breast when US was used with the compression grid. These results suggest that the potential for misidentification of masses with freehand US is real and that a mammographic grid localizat...