Follow-up imaging for unexpected liver lesions detected on baseline breast MRI is rarely necessary, according to new research published Tuesday in Clinical Imaging.

Incidental findings, discovered outside the original purpose of the exam, are common on breast magnetic resonance imaging, occurring in upward of 34% of cases. Lesions on the liver are the most encountered incidentaloma in these instances but are often benign. Still, fear of missing a metastasis may lead to additional imaging evaluation, delaying breast cancer treatment and incurring further healthcare costs.

New York City imaging experts recently set out to explore this issue, retrospectively analyzing breast MRI reports from a five-year period. Out of 131 individuals with liver lesions included in the study, only 3% had metastasized. All four were among women with a breast cancer diagnosis of at least stage 2, Memorial Sloan Kettering Cancer Center experts reported.

“As breast MRI becomes more utilized, which is anticipated with the increased use of screening breast MRI and abbreviated breast MRI, we ought to be careful of the additional imaging workup prompted by these screening exams,” Jill Gluskin, MD, an assistant attending radiologist in breast and body imaging, and co-authors wrote Feb. 15. “Given the low rate of malignant liver lesions on breast MRI, dedicated follow-up imaging may not be needed for every incidentally identified liver lesion.”

Gluskin et al. queried their hospital’s database searching for reports of all breast MRI exams performed between 2011-2016. They only included those who received an initial baseline breast MRI, coupled with subsequent abdominal imaging with the words “hepatic” or “liver” appearing in the report.

Across the study population, 72% of women underwent breast MRI for extent of disease evaluation, 19% for high-risk screening, 8% for implant evaluation and less than 1% for “problem solving.” Out of 131 incidental liver lesions, more than 89% were identified as benign on subsequent abdominal scans while 8% more were “probably benign.” The remaining four lesions (3%) were confirmed as breast cancer metastases. Such metastatic liver lesions were more likely for women with a current diagnosis of breast cancer than for women without one (4% vs. 0%). And similarly, metastatic liver lesions identified on breast MRI were more likely for patients with a higher prognostic stage (2 or 3) vs. a lower one (0 or 1) or no breast cancer at all (11% vs. 0%).

“This suggests that breast MRI indication and clinical staging of current breast cancer, if present, can help plan management and decisions to obtain additional imaging follow-up of liver lesions,” the authors concluded.