Identification of a localization wire tip in an occult breast lesion using a handheld magnetometer

Abstract

Background. The Sentimag hand-held probe detects the magnetic response from iron oxide particles trapped in a sentinel node. Objectives. To investigate if an electromagnetic probe can be helpful in the identification of a hook wire tip located in an occult breast lesion. Materials and methods. Forty-two patients undergoing lumpectomy without axillary procedure were enrolled. In all cases, suspicious non-palpable microcalcifications without mass were found, and a vacuum-assisted stereotactic biopsy was performed. On the day of surgery, a traditional localization wire (LW) was placed under imaging guidance. The Sentimag magnetometer was used to precisely detect the wire tip through the skin. Then, the skin incision was made and Sentimag was used again to guide the surgeon to the lumpectomy bed. The accuracy of excision was assessed with intra-operative specimen 3D tomosynthesis. Results. Median lesion size was 16 mm (range: 4-38 mm) and median depth was 33 mm (range: 14-78 mm). In all cases, the wire tip was successfully identified. Neither wire displacement nor transection occurred. Intraoperative radiography demonstrated doubtful margin requiring selective cavity shaving in 6 patients (14%). The need for cavity shaving was significantly influenced by the lesion size and histology: median size 30 mm (range: 24-38 mm) compared to 15 mm (range: 4-28 mm) and histology of ductal carcinoma in situ (DCIS) compared to atypical ductal hyperplasia (ADH) and lobular neoplasia (LN). Tumors requiring cavity shaving tended to be deeper - they had a median depth of 43 mm (range: 17-78 mm) compared to 32 mm (range: 14-76 mm) in patients who did not need cavity shaving, but this parameter was statistically significant. Conclusions. Intraoperative identification of the wire tip using Sentimag is a simple technique facilitating targeted excision without excessive removal of breast tissue. Since it is not associated with additional costs, it may be worth considering, particularly in developing countries.