Complete Excision of the MRI Target Lesion at MRI-Guided Vacuum-Assisted Biopsy of Breast Cancer

OBJECTIVE. The purpose of our study was to determine the frequency of complete removal of the imaging target at MRI-guided vacuum-assisted biopsy of breast cancer and to assess the residual cancer rate at surgery in these lesions. MATERIALS AND METHODS. With the approval of our institutional review board, retrospective review was performed of 416 consecutive lesions that underwent MRI-guided 9-gauge vacuum-assisted biopsy, of which 76 (18%) yielded cancer. Medical and pathology records were reviewed. RESULTS. Vacuum-assisted biopsy histology in 76 cancers was ductal carcinoma in situ in 39 (51%) and invasive cancer in 37 (49%). Median MRI lesion size in these 76 cancers was 1.2 cm (range, 0.4-8.0 cm). The median number of samples obtained was 12 (range, 6-24 samples). Among 76 cancers, the MRI target was completely excised in 23 (30% [95% CI, 20-42%]), sampled in 52 (69% [57-79%]), and possibly missed in one (1% [0-7%]). Complete MRI target excision rather than sampling was significantly more likely in lesions:! 1 cm than in lesions >1 cm (18/34 53% vs 5/41 = 12%; p < 0.001). Surgery, performed in 67 of 76 cancers, showed residual cancer in 55 (82% [71-90%]). The residual cancer rate was significantly lower if the MRI target was completely excised rather than sampled (14/22 = 64% vs 40/44 = 91%; p < 0.02). CONCLUSION. Complete excision of the MRI target occurred in 30% of breast cancers diagnosed at MRI-guided vacuum-assisted biopsy. Among cancers in which the MRI target was percutaneously excised, surgery yielded residual cancer in 64%. Complete removal of the MRI target does not ensure complete histologic excision of the cancer.