Clinical Utility of Breast MRI in the Diagnosis of Malignancy After Inconclusive or Equivocal Mammographic Diagnostic Evaluation

OBJECTIVE. The purpose of this study was to determine the clinical utility of breast MRI for diagnosing malignancy in women with equivocal mammographic findings but no symptoms. MATERIALS AND METHODS. Retrospective review of an institutional MRI database of 7332 contrast-enhanced breast MRI examinations from January 1, 2009, through December 31, 2012, yielded the records of 296 (4.0%) examinations of 294 women without symptoms who underwent MRI for mammographic findings uncertain at diagnostic evaluation. Imaging findings, histopathologic results, and patient demographics were obtained from the electronic medical record. RESULTS. The mean patient age was 55 years (range, 29-83 years). Mammographic lesion type (n = 294) included 89 focal asymmetries, 76 asymmetries, 64 masses, 44 architectural distortions, 17 surgical scar versus lesion, and four miscellaneous lesions. Diagnostic ultrasound, performed on 286 of 294 (97.3%) lesions at mammographic evaluation, showed an ultrasound correlate in 37 (12.9%) lesions, equivocal correlate in 48 (16.8%), and no ultrasound correlate in 201 (70.3%). MRI examination of 294 index lesions showed a correlate in 133 (45.2%) and no correlate in 161 (54.8%). Forty of 294 (13.6%) index lesions were malignant, 37 (92.5%) with an MRI correlate and three (7.5%) without an MRI correlate. Among 250 patients who underwent biopsy or had 2 or more years of imaging stability, the sensitivity, specificity, negative predictive value, and positive predictive value of breast MRI for malignancy were 92.5%, 62.4%, 97.8%, and 31.9%. Forty-four of 294 (15.0%) patients had lesions incidentally found at MRI; 7 of 41 (17.1%) lesions that were biopsied or were stable for at least 1 year were malignant. CONCLUSION. Problem-solving breast MRI for inconclusive mammographic findings helps identify malignancies with high sensitivity and a high negative predictive value.