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 < or = 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.