Incidental liver lesions seen on Breast MRI: When is additional imaging warranted?

Purpose: Incidental hepatic lesions identified on breast MR can be a diagnostic dilemma due to concern for liver metastases or other significant hepatic lesions. The purpose of this study was to identify the incidence and nature of liver lesions seen on breast MR, and determine if additional imaging is necessary. Methods and materials: Imaging reports of all breast MR examinations performed at our institution from January 1, 2010 to December 31, 2011 were reviewed to identify reports with hepatic abnormalities. Lesion characteristics, subsequent diagnosis, duration of follow up and additional imaging results (if performed) were all recorded. Results: Of 1664 breast MRs, incidental hepatic lesions were seen in 207 studies (12.4%) in 169 patients. In 154 of 169 patients (91.1%) the lesions were characterized as T2 hyperintense and clearly as bright as adjacent fat on T2-weighted or localizer sequences. 0 of these 154 lesions were clinically significant at clinical or radiological follow-up. In the remaining 8.9% (15 of 169), lesions were characterized as not as bright as adjacent fat on T2 weighted or localizer imaging. In two cases, lesions were confirmed as incidental hepatic metastatic disease. Conclusion: 91.1% of incidental hepatic lesions were circumscribed, T2 hyperintense lesions and characterised as clearly as bright as adjacent fat on T2 weighted imaging at additional review. None of which were clinically significant at clinical or radiological follow-up. We advocate that circumscribed T2 hyperintense lesions which are clearly as bright as adjacent fat on T2 weighted imaging are of unlikely clinical significance and follow-up imaging should not be recommended, reducing the rate of additional imaging from 37.3% to 5.3%.