MR-navigated ultrasound with supine breast MRI for suspicious enhancing lesions not identified on second-look ultrasound in breast cancer patients

Purpose: This study evaluated the usefulness of MR-navigated US for evaluation of MRI-detected lesions not visible on second-look US and analyzed differences of the lesion to nipple distance between supine and prone position.

Methods: Of the 831 consecutive patients who were diagnosed as breast cancer and examined with breast MRI from June 2013 to September 2015, we included 40 lesions in 37 patients who underwent MR-navigated US for MRI-detected lesions which were not visible on second-look US. First MRI was performed in prone position using a 1.5-T imager and second MRI was performed in a supine position for MR-navigated US.

Results: Of 40 lesions, 31 (78%) were identified with MR-navigated US, whereas 5 (13%) lesions disappeared on supine MRI and 4 (10%) showed no correlation on MR-navigated US. Of 31 lesions with pathologic confirmation, 7 (23%) were malignant, 2 (6%) were high risk lesions and 22 (71%) were benign lesions.

Comparing the US findings of benign and malignant lesions, orientation of the lesion showed significant difference (p = 0.045), whereas lesion shape, margin and echo pattern were not significantly different between two groups (p = 0.088, p = 0.094 and p = 0.412, respectively). Median difference of lesion to nipple distance on supine and prone MRI was 8 mm (0 – 34 mm) in horizontal direction and 5 mm (0 – 39.5 mm) in vertical direction. Thirteen lesions showed more than 1 cm difference in both horizontal and vertical direction.

Conclusion: MR-navigated US is useful for the evaluation of MRI-detected lesions which were not visible on second-look US in breast cancer patients.