MR imaging in probably benign lesions (BI-RADS category 3) of the breast

To investigate the role of dynamic magnetic resonance (MR) imaging in the evaluation of probably benign lesions (BI-RADS category 3) and its contribution to patient management.

Dynamic breast MR imaging was performed in 56 lesions assessed as probably benign in mammography of 43 patients. In MR imaging, T2-weighted turbo spin echo (TSE) with fat suppression sequence followed by pre- and post-contrast T1-weighted 3D-FLASH sequences were used. MR imaging findings were scored using 0-2 point criterion scale. The lesions were divided into five groups according to their total score (0 point: group 1, negative; 1-2 points: group 2, benign; 3 points: group 3, probably benign; 4-5 points: group 4, suspicious for malignancy; 6-8 points: group 5, highly suggestive of malignancy). Histopathologic verification of lesions in group 4 and above was obtained. Lesions in group 3 were either biopsied or followed up by mammography or MR imaging. Lesions in group 1-2 were followed by mammography of 6-month intervals for 2 years. The sensitivity, specificity, accuracy, and positive and negative predictive values of MR imaging in the determination of malignancy in BI-RADS category 3 lesions were calculated.

Fifty-six findings (45 mass, 9 breast tissue, 2 focal enhancement) in 43 patients were detected in MR imaging. According to their total score, 41 lesions (73.2%) and breast tissue had 0 point (group 1); 10 lesions (17.8%) had 1-2 points (group 2); 2 lesions (3.6%) had 3 points (group 3); 2 lesions (3.6%) had 4 and 5 points (group 4); and 1 lesion (1.8%) had 6 points (group 5). Ten lesions (of six in groups 1 and 2, one in group 3, three in groups 4 and 5) were histopathologically confirmed. Out of 10 lesions, only 1 (1.8%) with 4 points in group 4 was diagnosed as invasive ductal carcinoma. Other lesions followed with mammography or MR imaging did not change. The sensitivity, specificity, accuracy, positive and negative predictive values of MR imaging in the determination of malignancy in BI-RADS category 3 lesions were calculated as 100, 96.4, 96.4, 33.3, and 100%, respectively.

In the evaluation of BI-RADS category 3 lesions, dynamic MR imaging does not provide additional information with low positive predictive value similar to that of short interval mammography follow-up.