Complete percutaneous excision of infiltrating carcinoma at stereotactic breast biopsy: how can tumor size be assessed?

OBJECTIVE The purpose of this study was to determine the frequency of complete excision of infiltrating carcinoma at stereotactic 11-gauge directional vacuum-assisted breast biopsy and to evaluate the feasibility of measuring tumor size in stereotactic biopsy specimens in infiltrating carcinomas that were percutaneously excised. MATERIALS AND METHODS We performed retrospective review of 51 infiltrating carcinomas diagnosed using stereotactic 11-gauge directional vacuum-assisted biopsy that underwent subsequent surgery. For lesions yielding no residual infiltrating carcinoma at surgery, the maximal dimension of the tumor was measured in stereotactic biopsy specimens using ocular micrometry. RESULTS In 10 (20%) (95% confidence intervals, 9.8-33.1%) of 51 infiltrating carcinomas diagnosed at stereotactic biopsy, surgery revealed no residual infiltrating carcinoma. Complete excision of infiltrating carcinoma was more frequent if 14 or more specimens were obtained (32% versus 0%, p < .004), if the mammographic lesion was removed (35% versus 7%, p < .03), and if the mammographic lesion size measured 0.7 cm or less (50% versus 16%, p = .08). Tumor size in stereotactic biopsy specimens was within 3 mm of mammographic lesion size in six (60%) of 10 lesions, including five (71%) of seven masses and one (33%) of three calcification lesions, but was smaller than the mammographic lesion size in eight (80%) of 10 lesions. CONCLUSION Surgery revealed no residual infiltrating carcinoma in 10 (20%) of 51 infiltrating carcinomas diagnosed at stereotactic 11-gauge biopsy. Although tumor size can be assessed in stereotactic biopsy specimens in these lesions, such measurements may underestimate the maximal dimension of the tumor. Further study is needed to evaluate the usefulness of these measurements in guiding treatment decisions.