Utility of intraoperative frozen section examinations of surgical margins: implication of margin-exposed tumor component features on further surgical treatment

Objective: In patients who underwent breast-conserving surgery, we attempted to identify the histological characteristics of margin-exposed tumor components on intraoperative frozen section examinations that were predictive of residual tumor components in additionally resected specimens. Methods: Of 1835 patients who underwent breast-conserving surgery, we identified 220 patients who had positive surgical margins determined by intraoperative frozen section examinations and who had undergone immediate additional resections. Two observers (M.K., H.T.) reviewed the slides of frozen sections and confirmed the presence of tumor components. Results: In additionally resected specimens, residual tumors were detected in 115 cases (52.3%) but not in 105 cases (47.7%). The primary tumor characteristics of extensive intraductal component (+), younger age, invasive lobular carcinoma and pathological T3 classification were significantly associated with the residual tumor components. The margin-exposed tumor components of the maximum diameter, number of positive margins and histological type were correlated with the residual tumors. Multivariate analysis showed that the maximum tumor diameter was an independent risk factor for residual tumors. Conclusions: Diagnosis of positive margins by intraoperative frozen section examinations was useful for predicting residual tumors, and three histological properties of the margin-exposed tumor components were correlated with the status of residual tumor components. Although it was impossible to clearly identify the single main factor for predicting patients for whom additional resections were not necessary, it may be possible to consider stratification of additional surgical therapy according to the characteristics of margin-exposed tumor components on intraoperative frozen section examinations.