Utility of Targeted Sonography for Breast Lesions That Were Suspicious on MRI

OBJECTIVE: Data remain sparse to guide the use of targeted sonography for suspicious breast lesions found with MRI. The purpose of our study was to determine the usefulness of sonography in this setting. MATERIALS AND METHODS: Retrospective review of our breast MRI database was performed to identify all nonpalpable, mammographically occult MRI-detected suspicious lesions from January 1, 2003, to December 30, 2004, that underwent targeted sonography followed by imaging-guided biopsy. Frequency of sonography detection was determined, and MRI features (BI-RADS lesion type and size), histopathology outcomes, and positive biopsy rates of sonographically detected and occult findings were compared using chi-square analysis. RESULTS: Targeted sonography was performed for 167 of 201 MRI lesions. Outcomes were benign in 120 (72%) and malignant in 47 (28%) findings. Lesions assessed on sonography were 84 (50%) masses, 53 (32%) nonmasslike enhancements, and 30 (18%) foci, with mean size of 16 mm. Overall, 76 of 167 (46%) lesions were detected with sonography. Depiction was significantly more frequent for masses (58%) than for nonmasslike enhancement (30%) or foci (37%) (p = 0.003). Lesion size did not affect the frequency of detection. Sonographically depicted findings had a significantly higher positive biopsy rate (36%) than sonographically occult lesions (22%) (p = 0.05). CONCLUSION: Targeted sonography detected nearly half (46%) of MRI lesions evaluated, with depiction being most frequent for masses. Sonographically occult lesions had a probability of malignancy (22%), which warrants biopsy despite lack of sonographic detection.