Effect of Intraoperative Imprint Cytology Followed by Frozen Section on Margin Assessment in Breast-Conserving Surgery.

PURPOSE Intraoperative margin assessment can reduce positive margins in patients undergoing breast-conserving surgery. However, reports on intraoperative margin assessment have described only the use of either imprint cytology or frozen section. This study was designed to elucidate the effect of intraoperative margin assessment using imprint cytology followed by frozen section. METHODS Overall, 522 patients were enrolled. First, the entire surgical margin was subjected to imprint cytology. Frozen section was performed only in cases with "positive" or "suspicious" imprint cytology results. An additional intraoperative excision was performed in patients with frozen section-positive lesion sites. All margins were evaluated using postoperative permanent sections after excision. RESULTS Among 522 patients, 136 (26.1%) were imprint cytology-positive, and 386 (73.9%) were imprint cytology-negative. Among the 386 imprint cytology-negative patients not subjected to frozen section, 11 (2.1%) were permanent sections-positive (imprint cytology-false-negative). In 47 of the 136 imprint cytology-positive patients, additional intraoperative excision was unnecessary due to the frozen section-negative diagnosis. Moreover, these patients could avoid reoperation, because they were permanent section-negative. The false-positive rate of imprint cytology alone was 13.4%, but adding frozen section to imprint cytology decreased the overall false-positive rate to 2.5%. After undergoing excision, four patients still had positive margins. The overall positive margin rate in the final pathology based on permanent sections was 2.9% (15/522). CONCLUSIONS Imprint cytology followed by frozen section led to a markedly decreased positive margin rate. This is considered the best method for intraoperative margin assessment, as it can overcome the limitations of cytology and histology performed individually.