Tissue marking clip for stereotactic breast biopsy: initial placement accuracy, long-term stability, and usefulness as a guide for wire localization.

PURPOSE: To determine initial placement accuracy, long-term stability, and usefulness as a guide for wire localization for metallic marker clips placed percutaneously after stereotactic breast biopsy.
MATERIALS AND METHODS: One hundred forty-nine marker clips were placed percutaneously with a straight-needle or through-probe method, and clip positions were measured. The locations of 31 marker clips were followed up from deployment to first follow-up mammography. Thirty-six biopsy sites with marker clips were excised surgically and examined; 18 of these marker clips were targets for wire localization. The locations of 22 benign lesions were measured over time to calibrate the measurement system.
RESULTS: Baseline variability was 8 mm. Initial marker clip deployment averaged 5 mm above baseline from the center of the target lesion (P < or = .01). Compared with baseline variability, marker clips remained in place from initial deployment to first imaging follow-up (mean, 8.6 months). Potentially clinically meaningful misplacement rates (deployment > 24 mm from target lesion center) were 7% for the through-probe method and 11% for the straight-needle method (not significantly different; P = .33).
CONCLUSION: The marker clips appear to be useful targets for wire localization when the entire target lesion is removed at directional, vacuum-assisted breast biopsy. Upright, two-view mammography is recommended after deployment of the marker clip to document location.