Cancer yield of probably benign breast MR examinations

PURPOSE: To evaluate the cancer yield, frequency of use, and follow-up compliance of breast MR examinations assessed as "probably benign." MATERIALS AND METHODS: We retrospectively reviewed our MR database of 809 consecutive examinations between January 2003 and June 2004. We identified all examinations that ultimately received an MR breast imaging reporting and data system (BI-RADS) 3 assessment and recommendation for a short-interval follow-up MR with or without an antecedent targeted ultrasound. The clinical indication for breast MR, date of the follow-up examination, follow-up assessment, and any pathology findings through June 2005 were collected from clinical records and radiology and pathology reports. Frequency of BI-RADS 3 use, follow-up compliance, and cancer yield were calculated. RESULTS: A total of 160 out of 809 (20%) examinations comprise the study population. A total of 100 out of 160 (63%) women returned for the recommended follow-up MR, in which three out of 100 (3%) were upgraded to BI-RADS 4 with biopsy recommended. One patient underwent biopsy and the result was benign. A total of seven out of 160 (4%) underwent mastectomy in lieu of MR for known cancer elsewhere in the breast. One out of seven mastectomy specimens contained malignancy that corresponded to the probably benign finding, resulting in a cancer yield of one out of 160 (0.6%). CONCLUSION: Our data suggest that follow-up MR is a valid alternative to biopsy for MR BI-RADS 3 lesions.