Implications of accurate pathologic margins in the treatment of primary breast cancer.

Eighty-seven patients who underwent mastectomy or reexcision following a previous segmental resection with pathologic margins evaluated at that time were restudied following their definitive therapy. Of these, 40 (46.0%) had involved margins, 28 (32.2%) had close margins, and 19 (21.8%) had clear margins. Residual tumor was subsequently found in 21 (52.5%) of 40, nine (32.1%) of 28, and five (26.3%) of 19, respectively. Analysis of specimens for quadrant of residual tumor showed 27 (31.0%) of 87 patients in the same quadrant, and 11 (14.7%) of 75 present in a different quadrant. The assessment of microscopic margins may be misleading since 29.8% (14/47) of patients with clear or close margins subsequently had residual tumor, and 47.5% (19/40) of those with involved margins had no residual tumor found. Further studies are essential to define the optimum guidelines for tumor excision at the time of segmental resection.