US findings of bilateral primary breast cancer: retrospective study.

For women with breast cancer, the contralateral breast is at high risk. The bilateral cancers may be synchronous or metachronous. If the bilateral breast cancers have similar ultrasonography (US) appearances, the US findings of the first breast cancer (index cancer) might lead to early detection of the contralateral cancer. The purpose of this study was to identify the US characteristics of bilateral breast cancer and to determine whether bilateral breast cancers have similar US appearances and whether the US findings for one breast cancer might be predictive of the contralateral breast cancer.We retrospectively reviewed the US manifestations of 58 patients with surgically proven bilateral primary breast cancer and compared the contralateral cancer with the index cancer by evaluation the margin, shape, inside echoes, posterior attenuation, calcification and color flow signals of 58 lesion pairs to investigate whether the bilateral breast cancers have similar US appearances.Bilateral primary breast cancers were more located in upper outer quadrant, frequently spiculation, taller than wide shape, with irregular margin, heterogeneous internal echo and acoustic shadowing, containing microcalcification and abundant color flow signals. The most common US appearances were taller than wide shape (75.0%, 87/116), irregular margins (79.3%, 92/116) and heterogeneous internal echo (86.2%, 100/116). Of the total 58 lesion pairs, 18 (31.0%) pairs had similar US characteristics, whereas 40 (69.0%) pairs had different US characteristics.US signs of the index cancer do not indicate the most likely appearance of the second cancer in the contralateral breast. Evaluation of the contralateral cancer should be performed without regard for the US findings for the index cancer.