Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA, 02115, USA; Department of Imaging, Dana-Farber Cancer Institute, Harvard Medical School, 450 Brookline Avenue, Boston, MA, 02215, USA. Electronic address: [Email]
OBJECTIVE : To determine the accuracy of magnetic resonance imaging (MRI)-directed breast ultrasound and subsequent ultrasound-guided biopsy, and to evaluate patient and lesion factors associated with the detection of an ultrasound correlate for MRI findings. METHODS : Health Insurance Portability and Accountability Act (HIPAA)-compliant, institutional review board-approved retrospective review of 7,332 consecutive contrast-enhanced MRI examinations from 1 January 2009 to 30 March 2012 was performed to identify MRI-detected lesions that underwent MRI-directed ultrasound, ultrasound-guided core-needle biopsy (USG-CNB), and follow-up MRI after benign biopsy. Examinations were reviewed in consensus. USG-CNB was considered accurate if the biopsy clip was within 1 cm of the MRI lesion on follow-up MRI. Medical records were reviewed for histopathology, patient demographics, and follow-up imaging. RESULTS : MRI-directed ultrasound was performed on 522 patients with MRI-detected findings. A presumed ultrasound correlate was identified in 298 cases and 221 (73.4%) underwent biopsy. Follow-up MRI after USG-CNB was performed for 90 benign concordant biopsied lesions. Seven lesions were excluded because the biopsy marker was not visible on the subsequent MRI examination. Of the remaining 83 lesions, the biopsy marker was accurate in 72 (87%) lesions on follow-up MRI and 11 were considered inaccurate (13%). Of these 11 lesions, five were considered benign based on stability/resolution at follow-up MRI, while six underwent subsequent tissue diagnosis (mean time to tissue diagnosis: 13 months), with 1/6 (16.7%) malignancies. CONCLUSIONS : Although MRI-directed ultrasound is a reliable and accurate method to evaluate MRI findings, a 13% inaccuracy rate for MRI-directed ultrasound-guided biopsy was found. Therefore, for cases with uncertain MRI-directed ultrasound correlation, MRI-guided biopsy should be performed for accurate and timely diagnosis.