Negative surgical margins in breast conserving surgery are critical to reduce local recurrence of breast cancer [18–20], and the local control of breast cancer is an essential factor in oncologic outcome because it may prevent distant metastasis. Although the surgical margin can be confirmed on the final pathologic reports, a re-operation would be needed when if positive surgical margins are identified. If the surgical margin can be confirmed during surgery, only re-excision under general anesthesia is needed to secure negative results.
Many breast surgeons use the intra-operative frozen sections to evaluate surgical margin [1, 2, 7]. However, the frozen section for margin assessment requires time and effort on the part of the pathologist which prolongs the operation. Therefore, researchers have tried to predict the margin status using imaging modalities, including specimen mammography, tomosynthesis, and IOUS, to overcome these shortcomings [9, 12, 21–23]. However, most of these are 2D imaging modalities, and their results for the closest distance between tumor and surgical margin would be different compared to the true margin; this is particularly true for specimen mammography because of compression technique, but there are some differences depending on clinics. In addition, because the sonographic images cannot detect an existence of microscopic tumor, a pathologic margin assessment cannot be completely omitted. The authors assumed that a certain distance can be a standard point which has a high probability of positive or negative potential in margin assessment. Then, the number of frozen sections can be reduced, which may lead to reduced surgery duration and reduced burden to the pathologists.
In a recent study, the closest distance was shorter in specimen mammography than in specimen ultrasound and final pathologic reports in both DCIS and IDC groups. Clingan et al. reported that the TM–RM distance of specimen mammography could be distorted by compression of specimen . Conversely, the closest margins of specimen ultrasound showed a similar pattern as those of the final pathologic report. In addition, although the possibility of margin positivity was higher when the closest margin was less than 1.8 mm (1.78 mm in DCIS, 1.02 mm in IDC), the possibility of margin negativity was significantly higher when the closest TM–RM distance was larger than 4 mm (3.97 mm in DCIS, 3.82 mm in IDC). Therefore, the surgeons can carefully skip the frozen sections in which direction the TM–RM distance is more than 4 mm of safety margin.
The authors suggest that the frozen section for margin assessment should be obtained from the cavity in the surgical field by the surgeons themselves. It would be difficult for other physicians, except the surgeon, to have an accurate orientation about the directions of the specimen.
Although the current study provides information on when the frozen sections are needed for margin assessment during surgery, there are several limitations. If a frozen section can be omitted, the operation time and pathologist’s burden can be reduced. However, the frozen section cannot be completely omitted in breast conserving surgery to evaluate the status of surgical margins. Several studies reported the results of fluorescence-guided margin assessment in breast conserving surgery to compensate for this disadvantage [25–28]. However, a specific device and agent are necessary to conduct such studies. Another limitation of this study is that the closest TM–RM distance of each technique could not be exactly matched in comparison, which is a common limitation in retrospective studies. More accurate data could have been produced if the tissue could be sampled or measured only in the same direction by staining or placing a clip. However, it is possible to assume that a similar position would have been measured without necessarily indicating the position.