Intraoperative specimen ultrasonography as a tool for real-time margin assessment in breast-conserving surgery

Adequate margin clearance is a key determinant of local control after breast-conserving surgery (BCS), yet dedicated intraoperative margin assessment is not available in all settings. Intraoperative specimen ultrasonography (IOUS) is widely accessible and can be performed by the surgeon. We evaluated the diagnostic accuracy of IOUS for detecting close or positive margins against permanent pathology, and its concordance with intraoperative pathological assessment.

In this prospective observational study, 60 consecutive patients undergoing BCS for invasive breast cancer were enrolled. The surgeons measured tumor-to-margin distances in six orientations by IOUS, while the pathologist, blinded to the measurements, performed gross assessment and the intraoperative re-excision decision. The permanent paraffin margin of the primary specimen served as the reference standard, with a close margin defined a priori as <2 mm. Diagnostic performance was assessed at the patient level using ROC analysis and at the 2 mm threshold, and at the margin level using generalized estimating equations to account for within-patient correlation. Agreement was evaluated with Bland-Altman analysis and the intraclass correlation coefficient (ICC).

Among 60 patients a positive margin was present in 5 (8.3%) and a close margin (<2 mm) in 17 (360 margins) (28.3%). The minimum IOUS margin discriminated close margins with an AUC of 0.779 (95% CI 0.637-0.921). At the patient level, using the 2 mm threshold, IOUS correctly identified 10 of 17 close-margin patients, with a sensitivity of 58.8% and specificity of 86.0%. Compared with the pathologist's re-excision recommendation (sensitivity 76.5%, specificity 76.7%), no significant difference was detected (McNemar, p = 0.167), although the study was not powered for equivalence; IOUS was less sensitive but more specific. At the margin level, each 1 mm increase in the IOUS margin distance was associated with a 36% reduction in the odds of that margin being in the close (OR 0.64, 95% CI 0.50-0.82; p <0.001).

Surgeon-performed IOUS provides intraoperative margin assessment with no significant difference from the pathologist's evaluation. It may serve as a practical, accessible adjunct where immediate intraoperative pathology is not available, though it cannot fully replace definitive histopathological assessment.