Andy Anderson MD, Abstract Co-Author: Nothing to Disclose

Sujata Vijay Ghate MD, Presenter: Nothing to Disclose

Jay Alan Baker MD, Abstract Co-Author: Research Consultant, Siemens AG

Sora Christina Yoon MD, Abstract Co-Author: Nothing to Disclose

To evaluate BI-RADS 3 MRI lesions and accurately characterize them using the latest BI-RADS MRI lexicon.

We retrospectively reviewed breast MRI exams with final assessment of probably benign (BI-RADS 3) from among 4,279 consecutive breast MR exams performed between Jan. 2005 and Dec. 2009. Studies with at least 2-years follow-up imaging confirming stability or resolution of lesion and cases with biopsy confirmation were included. Cancer yield was compared to imaging characteristics.

Of 4,279 breast MR exams, 282 (6.6%) with 332 lesions were assessed as BI-RADS 3. 280 lesions [121 (43.2%) foci, 84 (30.0%) masses and 74 (26.4%) non-mass enhancements (NME)] had adequate follow up. 12 of 280 lesions were malignant with a cancer yield of 4.3%. One (0.4%) lesion was characterized as nipple retraction and skin thickening. Foci were characterized as multiple (at least 3) or individual (fewer than 3). None of the 52 cases of multiple foci were malignant regardless of kinetics. Of 69 individual foci, 3 (4.3%) were malignant, including 1.9% (1 of 53) with persistent kinetics and 12.5% (2 of 16) with plateau or washout kinetics (ns; p=0.13; Fischer Exact test). Among all NME labeled probably benign, 5.1% (3 of 61) with persistent enhancement were malignant compared with 18.8% (3 of 13) with plateau or washout kinetics which approached statistical significance (p=0.06). NME was further characterized as symmetric vs asymmetric. No cases (0 of 16) of symmetric NME were malignant compared with 10.5% (6 of 58) of asymmetric NME (ns;p=0.22). Among asymmetric NME, 6.4% (3 of 47) with persistent enhancement were malignant compared with 27.3% (3 of 11) with plateau or wash-out kinetics (ns; p=0.075). For 84 masses assigned BI-RADS 3, 3.4% (2 of 61) demonstrating persistent, 0% (0 of 14) plateau, and 11.1% (1 of 9) washout kinetics were malignant (ns; p=0.37).

The 4.3% risk of malignancy for these MR BI-RADS 3 lesions is slightly higher than the accepted 2% risk for mammographic lesions. Results suggest kinetics should be considered when assigning BI-RADS 3 final assessment, particularly for foci and NME, although a larger sample size could confirm these findings.

Further knowledge of imaging characteristics and outcomes of BI-RADS 3 lesions on breast MRI could help determine which lesion features are appropriate for placement into this category.

Anderson, A, Ghate, S, Baker, J, Yoon, S, Frequency of Malignancy and Imaging Characteristics of Probably Benign Lesions Seen on Breast MRI.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13015160.html