Breast J. 2020;00:1–7. wileyonlinelibrary.com/journal/tbj | 1 © 2020 Wiley Periodicals LLC 1 | INTRODUCTION Increased rates of breast cancer screening across Canada and use of novel imaging techniques have improved detection rates of nonpalpable breast lesions. 1 The most common method for localizing non-palpable breast lesions is wire-guided localization (WGL). 1 This procedure uses a fine hooked wire loaded in a needle and inserted into the target lesion or area under image guidance (Figure 1). The position of the target lesion in relation to the wire is demonstrated in Received: 8 July 2020 | Revised: 2 November 2020 | Accepted: 4 November 2020 DOI: 10.1111/tbj.14115 ORIGINAL ARTICLE Adequacy of invasive and in situ breast carcinoma margins in radioactive seed and wire-guided localization lumpectomies Wyanne Law MD 1 | Xingshan Cao PhD 2 | Frances C. Wright MD, MEd, FRCPC 3 | Elzbieta Slodkowska MD, FRCPC 4,5 | Nicole Look Hong MD, MSc, FRCPC 6,7 | Belinda Curpen MD, FRCPC 8 1 Diagnostic Radiology Resident, University of Toronto, Sunnybrook Health Sciences Centre, Toronto, ON, Canada 2 Department of Research Design and Biostatistics, Sunnybrook Research Institute, Toronto, ON, Canada 3 Department of Surgery, Sunnybrook Health Sciences Centre, Toronto, ON, Canada 4 Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada 5 Department of Laboratory Medicine and Molecular Diagnostics, Sunnybrook Health Sciences Centre, Toronto, ON, Canada 6 Evaluative Clinical Sciences, Odette Cancer Research Program, Sunnybrook Research Institute, Toronto, ON, Canada 7 Division of Surgical Oncology, Sunnybrook Odette Cancer Centre, Toronto, ON, Canada 8 Department of Breast Imaging, Sunnybrook Health Sciences Centre, Toronto, ON, Canada Correspondence Wyanne Law, Diagnostic Radiology Resident, University of Toronto, Sunnybrook Health Sciences Centre, M6-263, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada. Email: wyanne.law@gmail.com Abstract Image-guided preoperative localizations help surgeons to completely resect nonpal- pable breast cancers. The objective of this study is to compare the adequacy of speci- men margins for both invasive breast cancer (IBC) and ductal carcinoma in situ (DCIS) after radioactive seed localization (RSL) vs wire-guided localization (WGL). We ret- rospectively reviewed 600 cases at a single Canadian academic center from January 2014 to September 2017, comparing surgical margins, re-excisions and reoperations, localization accuracy and major complications (migration, accidental deployment, vasovagal reaction), as well as operative duration between RSL and WGL cases. IBC margins were positive in 7% of RSL and 6% of WGL cases (P = .57). Tumor size (P = .039) and association with DCIS (P = .036) predicted positive margins in invasive carcinoma. DCIS margins were positive in 6% and 8%, and close (≤2 mm) in 37% and 36% of cases (P = .45) for RSL and RSL cases respectively. The presence of extensive intraductal component predicted positive DCIS margins (P < .0001). There was no significant difference between intraoperative re-excisions (P = .54), localization ac- curacy (P = .34), and operation duration (P = .81). Reoperation for lumpectomies and mastectomies was marginally higher for WGL than RSL (P = .049). There were 11 (4%) WGL and no RSL complications (P = .03). Overall, positive margins for IBC, close or positive margins for DCIS, intraoperative re-excision, localization accuracy, and operation duration were similar between RSL and WGL. The reoperation rate was higher in WGL than RSL, which may reflect practice changes over time. RSL was safer than WGL with lower complication rates. KEYWORDS breast cancer, radioactive seed localization, reoperation rates, surgical margins, wire localization