Breast implants are contraindicated only if the implant precludes the required research biopsies or interferes with palpating the breast lesion Patients with implants in the chest region that contain metal or conductive materials (e.g., metal implants, rods, or plates) which Varian Medical considers will interfere with the Calypso System's electromagnetic localization Contraindication to MRI (metal implants) Radiotherapy must begin within 12 weeks of last surgery (breast or axilla) or last chemotherapy\r\n* Note: Breast implants and expanders allowed Patient with breast implants (does not include patients having implants placed AFTER intra-operative radiotherapy) No ferromagnetic prostheses. Patients who have metallic surgical implants that are not compatible with an MRI machine are not eligible. Electrical implants such as cardiac pacemakers or perfusion pumps Prosthetic implants in the pelvic region that contain metal materials (e.g., an artificial hip) Breast implants; (patients who have implants removed are eligible) Inner ear implants Implants in the operated breast. Presence of breast implants Willingness and ability to schedule mastectomy 21-28 days following start of study agent; women with breast implants may participate Breast implants (patients who have had implants removed are eligible) Patients with breast implants are excluded. Patients with metal implants less than 5 cm from the treatment Implants in the operated breast Undergoing bilateral mastectomy reconstruction with tissue expanders (ipsilateral therapeutic/contralateral prophylactic) planned to be exchanged for breast implants Subjects with breast implants or a history of prior breast implants Metal implants for the treatment extremity History of a medical condition or procedure that is contraindicated for fMRI scanning (i.e. cardiac pacemaker, sternal wires, or metal implants); and For local participants undergoing bioelectrical impedance measurements: pregnancy, metal implants, and defibrillator implants Patient has metal implants near the surgical site that preclude treatment with the microwave system Patients with implantable pacemakers and other electronic implants, in accordance with Instructions for Use (IFU). Patients must not currently have breast enhancements (e.g., implants or injections) EXCLUSION - PATIENT: Breast implants (silicone or saline) Women with implants Imaging sets with implants Breast implants Women with bilateral breast implants or tram flap reconstruction Patients with breast implants Women with breast implants Bilateral breast implants or autologous breast flap reconstruction Metal implants on same limb as intended administration site Women with bilateral breast implants or tram flap reconstruction Bilateral breast implants Subjects with breast implants Bilateral breast implants. Prior breast reduction surgery is allowed. Have electrically, magnetically, or mechanically activated implants including cardiac pacemaker, cochlear implants, magnetic surgical clips or prostheses. Bilateral breast implants Breast implants at time of diagnosis; Note: patients who have had implants previously removed prior to diagnosis are eligible Have electrically, magnetically, or mechanically activated implants including cardiac pacemaker, cochlear implants, magnetic surgical clips or prostheses Have breast implants MR-incompatible metal implants Presence of metal implants Patients with breast implants or expanders Metallic implants Metallic implants (contraindicated for MRI) Implants in the chest region that contain metal or conductive materials (e.g., metal implants, rods, or plates) which Calypso Medical considers will interfere with the Calypso System's electromagnetic localization Patients with surgical implants and/or metallic foreign bodies non-compatible with the MR magnet Patient received a permanent prostate brachytherapy implant within the last 3 months (for palladium [Pd]-103 implants) or 12 months (for iodine [I]-125 implants) Metal implants in field of view Metallic implants (contraindicated for MRI) Metallic implants (contraindicated for MRI) Electrical implants such as cardiac pacemakers or perfusion pumps Patients with breast implants Electrical implants such as cardiac pacemakers or perfusion pumps Metallic implants Metallic implants Contraindication to MRI (metal implants) Have electrically, magnetically, or mechanically activated implants that would preclude MRI Breast implants allowed Patients with implants in the chest region that contain metal or conductive materials (e.g., metal implants, rods, or plates) which the Sponsor considers will interfere with the Calypso System's electromagnetic localization (note that the Sponsor will review a patient's implanted metal on a case by case basis).