Context: 40% of breast surgery patients have a lesion that requires preoperative localization, a process that demands close cooperation between radiological and surgical team. Magnetic seed localization is a new tracking technique which does not require programming the day before or on the day of the intervention. The aim of our study was to evaluate the efficacy and safety of magnetic localization of non-palpable breast lesions. Methods and patients: This is a study of 39 consecutive preoperative ultrasound-guided implantations of a magnetic seed (MS) in 37 patients, for non-palpable breast lesions, performed at the Breast Center at Saint-Joseph Hospital in Paris, France, between May 15th and December 21st, 2018. One patient who was operated on for papillomatous lesions had a double magnetic seed implanted. In the operating room, the MS was percutaneously localized by a magnetic probe. The ex-vivo magnetism was noted and the removed tissue was sent to radiology to look for the MS, after which it was sent for histopathological examination. All localized lesions had previously been biopsied, and there were 29 infiltrative cancers, 7 atypical lesions, and 3 benign lesions. The sentinel node was identified by super paramagnetic iron peroxide in 11 cases, and by isotopes in the 18 others. Results: Our patients were on average 57 years old (33-86 years old). All magnetic localization was realized using ultrasound. The mean ultrasound size of the lesions was 12.7 mm (5-34mm). The period of time from implantation to surgery varied from 0 to 21 days. The localization method was characterized by a rapid pose, facilitated by the excellent luminosity of the needle for the tracking. No compression pad was needed, optimizing the implementation and quality of the control mammography. The mean time for the tissue resection from incision to excision was 15 minutes for the first 10 cases. On the radiography of removed tissue: the clip was present in 38 out of 39 cases. One failure was registered, in relation to loss of the clip, found in the tumorectomy limits, in the patient with the double localization procedure. However, the target was effectively removed and detected histo-pathologically. In the 13 cases of super paramagnetic iron peroxide, the sentinel node was identified each time. All biopsied lesions were removed, and in cancerous lesions, the surgical margins were healthy in all cases. Conclusion: The MS localization technique is reliable and safe. For the patient, the main interest is a simplified procedure without long-term damage of the skin; for the radiologist, the rapidity of the procedure; for the surgeon, a real time guide for localizing the target; and for the hospital, an eased organization with regard to preoperative tracking during ambulatory surgery, with implantations possible up to 1 month prior to surgery, for instance at the time of the radiological review. The main limit to MS’s development remains its cost.
