Dynamic high-spatial-resolution MR imaging of suspicious breast lesions: Diagnostic criteria and interobserver variability

OBJECTIVE, Our study was undertaken to develop diagnostic rules and to asse ss the reproducibility of dynamic and morphologic parameters for the ch;cha racterization of suspicious breast lesions using dynamic high-spatial-resol ution MR imagine. MATERIALS AND METHODS. Fifty-seven patients with suspicious mammographic or palpable findings underwent preoperative contrast-enhanced MR imaging of t he breast using a three-time-point method of acquisition. Each lesion was p rospectively analyzed by two independent radiologists for morphologic and v isual dynamic enhancement characteristics. A classification and regression tree was used to examine the optimal order, cutoff points, and combination of imaging parameters to build a diagnostic rule separating benign from mal ignant lesions using histopathology findings as the standard of reference, Kappa statistics were used to determine observer variability. RESULTS, Among 23 benign and 33 malignant lesions (12 invasive, three ducta l carcinomaa in situ, and 19 mined cancer), margin morphology (p = 0.001) a nd enhancement pattern (p = 0.001) were the most significant MR imaging fin dings for lesion characterization. Focal mass lesions were classified as ma lignant when spiculated margins or both the washout enhancement pattern and "nonsmooth" margins were present. Interobserver agreement was almost perfe ct for washout pattern and substantial for margin assessment. In the limite d population tested retrospectively, the diagnostic rule yielded a sensitiv ity and positive predictive value of 97% each and a specificity and negativ e predictive value of 96% each. CONCLUSION. The washout enhancement pattern combined with lesion margin ass essment on dynamic: contrast-enhanced high-resolution MR imaging of the bre ast allows reproducible lesion characterization and may be a highly specifi c diagnostic tool.