Assessing asymmetric enhancement on breast MRI: Besting the diagnostic challenge with imaging and clinical clues.

Breast magnetic resonance imaging (MRI) has the highest sensitivity for breast cancer detection compared to other breast imaging modalities such as mammography and ultrasound. As a functional modality, it captures the increased angiogenic activity of breast cancer through gadolinium-based contrast enhancement. Normal breast tissue also enhances, albeit in distinct patterns termed background parenchymal enhancement (BPE). Asymmetric enhancement, i.e., when one breast enhances more prominently than the other, can pose a diagnostic challenge for interpreting radiologists as distinguishing suspicious nonmass enhancement (NME) versus benign asymmetric BPE can be difficult. Correlating with patient history and imaging findings can help differentiate benign versus suspicious patterns of asymmetric enhancement. We present a collection of cases illustrating clues helpful for assessing asymmetric enhancement encountered on breast MRI.