Identification of Occult Breast Lesions Detected by Magnetic Resonance Imaging with Targeted Ultrasound: a Prospective Study

Objective: To verify the capacity of targeted ultrasound (US) to identify additional lesions detected on breast magnetic resonance imaging (MRI), but occult to initial mammography, US and clinical examinations.

Methods: This prospective study included 68 additional relevant breast lesions identified on MRI of 49 patients. As an inclusion criterion, breast US and mammography were required and performed up to six months before MRI. These lesions were then subjected to targeted "second-look" US up to 2 weeks after MRI, performed by one or two radiologists with expertise on breast imaging. Lesions were evaluated according to the established Breast Imaging Report and Data System (BI-RADS) lexicon.

Results: Targeted US identified 46/68 (67.6%) lesions revealed by MRI. No significant associations were observed between US identification and the type of lesion, dimensions, morphological characteristics and enhancement pattern according to MRI findings. Targeted US identified 100% of BI-RADS category 5 lesions, 90% of category 4 lesions, and just over 50% of category 3 lesions (p<0.05). There was significant agreement (p<0.001) between MRI and US BI-RADS classification for all three categories.

Conclusion: Targeted US can identify a large proportion of the lesions detected by breast MRI, especially those at high risk of malignancy, when performed by a professional with experience in both breast US and MRI.