Breast MRI wire-guided excisional biopsy: specimen size as compared to mammogram wire-guided excisional biopsy and implications for use.

BACKGROUND

Breast magnetic resonance imaging (MRI) has been implemented as a screening tool for early detection and as a diagnostic test in the management of breast cancer. Lesions identified by MRI but not amenable to conventional biopsy techniques require MRI wire-guided excisional biopsy (MRIbx). We hypothesized that more tissue would be resected with MRIbx compared to Mammobx. We also sought to evaluate factors that might predict the presence of breast cancer in patients undergoing MRIbx.

METHODS

We reviewed consecutive cases of breast MRIbx from 2004 to 2006 performed by seven surgeons. MRI was performed in patients with either a synchronous breast cancer or significant risk factors. Lesions visualized only by MRI underwent diagnostic MRIbx. The control group was comprised of consecutive cases that underwent diagnostic Mammobx during the same time period. The volumes of tissue resected, overall and by pathologic outcome, were compared.

RESULTS

Seventy-one patients, with a mean age of 48, underwent MRIbx. Eleven (15.5%) invasive breast cancers and eight cases (11.3%) of ductal carcinoma in situ (DCIS) were identified. The median volume of tissue resected was significantly greater than that in the Mammobx group (28.8 cm3 vs 21.1 cm3, respectively). DCIS-containing MRIbx specimens were significantly larger than benign or invasive cancer-containing specimens. There was no significant overall association between either the indication for MRIbx or the size of the MRI lesion and the frequency of cancer.

CONCLUSIONS

In patients undergoing breast MRIbx, 27% were found to have DCIS or invasive breast cancer. MRIbx was associated with significantly larger specimen volumes than Mammobx.