Can MRI Provide Greater Clarity of Suspected BI-RADS 3 Lesions?

While lesions in the third category of the Breast Imaging-Reporting and Data System (BI-RADS 3) remain challenging due to variation in findings for a “probably benign” diagnosis, a new study suggests that magnetic resonance imaging (MRI) may facilitate downgrading of nearly 10 percent of lesions categorized as BI-RADS 3 due to initial ultrasound findings.

In a retrospective cross-sectional study, published in European Journal of Radiology Open, researchers reviewed MRI and ultrasound findings of 123 breast lesions (median size of 9 mm) from 67 patients (median age of 38). The patients included women who had assisted reproductive therapy (ART), women with prior high-risk breast lesions and patients who had suspected BI-RADS 3 lesions on ultrasound that were “not compatible with the clinical breast exam,” according to the study.

The study authors noted 87 percent agreement (107 lesions) between MRI and ultrasound on the BI-RADS 3 diagnosis. However, for 9.8 percent of the breast lesions (12 lesions), MRI findings resulted in downgrading of the lesions to BI-RADS 2. The researchers said the discordance between ultrasound and MRI in some cases was multifactorial.

“In (ultrasound) examination, cystic lesions were assumed (to be) complicated lesions due to having internal echo and internal septa; however, in mRI, the cysts were seen as a fluid collection without enhancement and therefore were downgraded to BI-RADS 2 lesions,” wrote Nasrin Ahmadinejad, M.D., who is affiliated with the Advanced Diagnostic and Interventional Radiology Research Center (ADIR) at the Imam Khomeini Hospital and the Tehran University of Medical Sciences in Iran, and colleagues.

(Editor’s note: For related articles, see “What BI-RADS Changes Are on the Way for Breast MRI Reporting?” and “What a New Meta-Analysis Reveals About Breast Density, Mammography and MRI Screening.”)

For circumscribed hypoechoic masses on ultrasound, Ahmadinejad and colleagues said these lesions would be categorized as BI-RADS 3 but MRI revealed high T1 cysts without enhancement that were assumed to be high proteinaceous lesions or bloody cysts. They noted these lesions were subsequently downgraded to BI-RADS 2 lesions.

The researchers also noted MRI upgrading of lesions in four cases (3.3 percent) to BI-RADS 4. Ahmadinejad and colleagues recalled one case in which ultrasound findings revealed a dilated duct with a circumscribed intraductal mass that lacked vascularity. However, the original BI-RADS 3 categorization for this lesion was upgraded to BI-RADS 4 when MRI findings showed a cyst with a thick wall and enhancement of a heterogenous nature, according to Ahmadinejad and colleagues.

The study authors acknowledged the limited sample size being a key limitation of the study. They suggested that future studies could have larger data sets in order to incorporate more of a diversity of patterns and pathologies of BI-RADS 3 lesions, and possibly include mammography in the comparison of imaging modalities for these lesions.