Magseed Enabled Long-Term Localization of Axillary Lymph Nodes

Inclusion Criteria: * Age 18 years or older at time of consent * Histologically confirmed cT0-4, N1 breast cancer * Axillary lymph node metastasis with pathologic confirmation by needle biopsy * Clip placed in the sampled axillary lymph node before initiation of chemotherapy * Planned for neo-adjuvant chemotherapy prior to surgical resection * Eligible for targeted axillary dissection (defined as selective localization and removal of the clipped node and SLND) at the completion of neo-adjuvant chemotherapy * ECOG performance status 0-2 Exclusion Criteria: * Distant metastases * Inflammatory breast cancer * Prior ipsilateral axillary surgical procedure including SLND or axillary node excision * Prior history of breast cancer in the ipsilateral breast * History of lymphoma * Subject is pregnant * Previous radiation to the breast or axilla * Pacemaker or other implantable cardiac device in the ipsilateral chest wall