High resolution MRI of the breast at 3 T: which BI-RADS® descriptors are most strongly associated with the diagnosis of breast cancer?

OBJECTIVE: To identify which breast lesion descriptors in the ACR BI-RADS® MRI lexicon are most strongly associated with the diagnosis of breast cancer when performing breast MR imaging at 3 T.
METHODS: 150 patients underwent breast MR imaging at 3 T. Lesion size, morphology and enhancement kinetics were assessed according to the BI-RADS® classification. Sensitivity, specificity and diagnostic accuracy were assessed. The effects of the BI-RADS® descriptors on sensitivity and specificity were evaluated. Data were analysed using logistic regression. Histopathological diagnoses were used as the standard of reference.
RESULTS: The sensitivity, specificity and diagnostic accuracy of breast MRI at 3 T was 99%, 81% and 93%, respectively. In univariate analysis, the final diagnosis of malignancy was positively associated with irregular shape (p < 0.001), irregular margin (p < 0.001), heterogeneous enhancement (p < 0.001), Type 3 enhancement kinetics (p = 0.02), increasing patient age (p = 0.02) and larger lesion size (p < 0.001). In multivariate analysis, significant associations with malignancy remained for mass shape (p = 0.06), mass margin (p < 0.001), internal enhancement pattern (p = 0.03) and Type 3 enhancement kinetics (p = 0.06).
CONCLUSION: The ACR BI-RADS® breast lesion descriptors that are mostly strongly associated with breast cancer in breast MR imaging at 3 T are lesion shape, lesion margin, internal enhancement pattern and Type 3 enhancement kinetics. KEY POINTS: • 3 Tesla breast MRI allows an accurate diagnosis of breast cancer • The BI-RADS® descriptors help provide a confident diagnosis • The shape, margin, enhancement pattern and kinetics are the most important features • An irregular shape and margin, heterogeneous enhancement and type-3 kinetics indicate malignancy.