High-Spatial-Resolution 3-T Breast MRI of Nonmasslike Enhancement Lesions: An Analysis of Their Features as Significant Predictors of Malignancy

OBJECTIVE: The purpose of this study was to analyze the features of nonmasslike enhancement detected on 3-T MRI and to determine which of these features are significant predictors of malignancy. MATERIALS AND METHODS: Retrospective review was performed of 124 consecutive patients with nonmasslike enhancement detected on 3-T MRI after biopsy or surgery. We described nonmasslike enhancement using the descriptors in the BI-RADS MRI lexicon. In addition to the BI-RADS descriptors, whether clustered ring enhancement was present and whether surrounding high signal intensity (SI) was present on T2-weighted imaging were assessed. RESULTS: Cancer was identified in 85 lesions (69%). Of these lesions, ductal carcinoma in situ (DCIS) was found in 41 (48%) and invasive cancer in 44 (52%). The features found to be significant predictors of malignancy were segmental (p = 0.001), focal (p = 0.006), dendritic (p = 0.017), and clustered ring enhancement (p = 0.026) and surrounding high SI on T2-weighted imaging (p < 0.0001). The features found to be significant predictors of invasive cancer were dendritic enhancement (p < 0.0001) and surrounding high SI on T2-weighted imaging (p < 0.0001). There were no significant predictive features for DCIS. Homogeneous enhancement was found to be a significant predictor of benignancy (p = 0.001). Kinetic patterns were not significant predictors of malignancy. Nonmasslike enhancement of 1 cm or larger was more often malignant than lesions smaller than 1 cm (p < 0.0001). In multivariate analysis, a lesion size of 1 cm or larger was found to be the only significant predictor of malignancy for nonmasslike enhancement. CONCLUSION: Segmental, focal, dendritic, and clustered ring enhancement; surrounding high SI on T2-weighted imaging; and a lesion size of 1 cm or larger can act as predictors of malignancy for nonmasslike enhancement detected on 3-T MRI, but kinetic characteristics cannot.