Probably benign breast MRI lesions: frequency, lesion type, and rate of malignancy.

PURPOSE: To determine the frequency, malignancy rate, and imaging characteristics of BI-RADS (Breast Imaging Reporting and Data System) 3 MRI detected lesions. MATERIALS AND METHODS: A total of 4370 consecutive contrast-enhanced breast MRI exams from March 1, 2004, to March 1, 2009, were retrospectively reviewed. The study was HIPAA (Health Insurance Portability Accountability Act) compliant and Institutional Review Board approved. The frequency of BI-RADS 3 MRI interpretations and lesion type, as well as malignancy rate at follow-up were calculated. RESULTS: There were 348/4370 (8%) BI-RADS 3 exams performed on 345 patients. There were 125 foci (35.9%), 52 non-masslike enhancements (14.9%), and 171 masses (49.1%). There were 207 lesions with biopsy or imaging follow-up of at least 24 months (mean, 32 months; range, 6-77 months) of the BI-RADS 3 lesion. Five of these 207 (2.4%) lesions were found to be malignant. CONCLUSION: Rate of malignancy among BI-RADS 3 MRI exams with follow-up was 2.4%. Types of lesions assigned as probably benign were 35.9% foci, 14.9% non-masslike enhancements, and 49.1% masses.

Utility of targeted sonography in management of probably benign breast lesions identified on magnetic resonance imaging.

OBJECTIVES: The purpose of this study was to determine the utility of targeted sonography in the management of probably benign breast lesions detected on magnetic resonance imaging (MRI). METHODS: A total of 4370 consecutive contrast-enhanced breast MRI examinations from March 1, 2004, to March 1, 2009, were retrospectively reviewed. The study was Health Insurance Portability and Accountability Act compliant and Institutional Review Board approved. When targeted sonography was recommended for a Breast Imaging Reporting and Data System (BI-RADS) category 3 examination, results of the sonography and any subsequent breast pathologic examinations were recorded. The frequency of identifying the MRI-detected lesions and the rate at which the BI-RADS category was changed by sonography were calculated for mass and non-mass-like lesions. RESULTS: Of the 4370 examinations, 349 (8%) had BI-RADS 3 findings in 346 patients. One hundred eighteen lesions underwent targeted sonography for evaluation of 85 masses and 33 areas of non-mass-like enhancement. Of these 118 lesions, 54 (46%) were seen on sonography. No cancers were detected on sonography in the areas of non-mass-like enhancement. Two of the 85 masses (2.4%) evaluated with targeted sonography had a malignant diagnosis before initiation of follow-up. CONCLUSIONS: Selective use of targeted sonography, particularly in masses, may help identify some malignancies before initiating short-interval follow-up for MRI-detected BI-RADS 3 lesions.