Differential diagnosis of breast lesions 5 mm or less: is there a role for magnetic resonance imaging?

OBJECTIVES

According to magnetic resonance (MR) imaging Breast Imaging Reporting and Data System, foci are small enhanced lesions 5 mm or less in diameter. This study was conducted to (a) assess morphological and dynamic profiles in malignant versus benign foci in breast MR imaging (MRM) and to (b) identify overall diagnostic accuracy of MRM for differential diagnosis of foci.

METHODS

This study was approved by the local institutional review board; all patients gave written consent. All MRM (T1w-FLASH; 0.1 mmol/kg body weight gadolinium-diethylenetriamine penta-acetic acid; T2w-TSE; consecutive 12-year period; with histological verification after MRM were evaluated by 2 experienced (>500 MRM) radiologists in consensus using 16 predefined descriptors and were included into a database. A data set was created by extracting all lesions 5 mm or less (benign, 27; malignant, 61). Accuracy of individual descriptors was assessed (Crosstabs, chi2-test; positive/negative likelihood ratios (LR+/-); diagnostic odds ratio [DOR]). Binary logistic regression analysis was applied to identify overall diagnostic accuracy using all descriptors combined (area under the receiver operating characteristic curve,).

RESULTS

Washout was typically associated with malignancy (P < 0.05; DOR, 3.5). Irregular shape was feasible for differential diagnosis of foci (DOR, 7.3), yet majority of malignancies demonstrated a round shape (55.6%). Additional descriptors such as blooming (DOR, 4.0, LR+, 2.8), adjacent vessel (DOR, 4.8; LR+, 4.5), and root sign (DOR, 5.6; LR+, 4.1) showed a high accuracy. Overall accuracy for differentiation of benign versus malignant foci showed an area under the curve of 0.887 (P = 0.0001).

CONCLUSIONS

Assessment of dynamic and morphological profiles in foci 5 mm or less was feasible. Using all descriptors combined, a high potential for differential diagnosis of foci in magnetic resonance-mammography could be identified.