Contralateral enhancing lesions on magnetic resonance imaging in patients with breast cancer: role of second-look sonography and imaging findings of synchronous contralateral cancer.

OBJECTIVES: The purposes of this study were to assess the clinical utility of sonography for evaluation of contralateral suspicious lesions detected on magnetic resonance imaging (MRI) in patients with breast cancer and to compare imaging findings of the index and synchronous contralateral cancers. METHODS: We performed breast MRI on 853 consecutive patients with histologically confirmed breast cancer between January 2006 and December 2009. All patients underwent mammography and whole-breast sonography before MRI. We included 126 contralateral enhancing lesions in 98 patients who underwent second-look sonography. Lesions with sonographic correlation were biopsied using sonographic guidance, and lesions without sonographic correlation were biopsied using computed tomographic guidance or followed with imaging modalities. RESULTS: Of 126 suspicious lesions, 81 (64%) were correlated on sonography, and 45 (36%) were not. Of 81 correlated lesions, 16 (20%) were malignant, and 65 (80%) were benign. Of 45 lesions that were not correlated on sonography, only 1 (2%) was malignant. Of 17 contralateral cancers, 11 were detected on initial sonography and 5 on second-look sonography. The index and contralateral cancers showed statistically significant differences in the sonographic boundary (P = .003) and posterior echogenicity (P = .013). The contralateral cancers detected on initial or second-look sonography showed significant differences in the echo pattern (P = .001). CONCLUSIONS: Magnetic resonance imaging is a reliable tool for detection of occult contralateral breast cancer. With second-look sonography, we can find additional contralateral cancer. When enhancing lesions on MRI are not correlated on sonography, MRI- or computed tomography-guided biopsy or short-term imaging follow-up should be done.