Metastases to the Breast from Non-mammary Malignancies: Primary Tumors, Prevalence, Clinical Signs, and Radiological Features

Rationale and Objectives: Most secondary intramammary tumors occur as metastatic involvement from the contralateral breast. Breast metastases (BM) from nonmammary malignancies are very rare. The aims of this study were to estimate retrospectively the prevalence of BM from nonmammary malignancies and to describe their radiologic appearance. Materials and Methods: BM were identified in 51 patients, including 43 women and eight men with a median age of 61 years (range, 24-84 years). Computed tomography of the thoracic region identified 108 lesions in 38 patients. Mammography was available for 37 patients (54 lesions). Ultrasound evaluation was performed in 43 patients (71 lesions). In 24 patients (93 lesions), magnetic resonance imaging of the breast was done. Images were reviewed in consensus by two radiologists according to the Breast Imaging Reporting and Data System lexicon. Results: The prevalence of BM in several tumors ranged from 0.12% to 4.92%. On computed tomography, most metastases were round or oval in shape with marked or moderate enhancement. On mammography, solitary or multiple round or oval masses with circumscribed margins were the most common pattern of BM. Ten percent showed microcalcifications. On ultrasound, most BM were hypoechoic, oval or round in shape, with microlobulated or circumscribed margins, and posterior acoustic enhancement. Doppler imaging showed hypervascularity in 39% of BM. On magnetic resonance imaging, most lesions demonstrated marked homogenous contrast enhancement. Type 1 kinetic curve was seen in 18%, type 2 in 52%, and type 3 in 30%. Conclusions: The radiologic features reported in this study should be taken into consideration in the differential diagnosis of breast lesions.