Statement: Patients with implantable cardioverter defibrillators are excluded from the primary trial.
Primary_evidence: Inclusion Criteria:   Participant is willing and able to give informed consent for participation in the study;   Female, aged 18 years or above;   Diagnosed with breast cancer (invasive or dcis);   Willing to allow his or her General Practitioner and consultant, if appropriate, to be notified of participation in the study;   Undergoing mastectomy breast surgery. Exclusion Criteria:   Patients with a Pacemaker or implanted device;   Patients requiring an MRI scan prior to surgery;   Patients with known coagulopathy or receiving anticoagulant medication including warfarin, heparin, clopidogrel or rivaroxaban;   Patients receiving Neoadjuvant chemotherapy;   Patients who are pregnant or lactating;   Patients scheduled for immediate breast reconstruction;   Patients who have received Sienna (iron oxide) injection in the previous six months;   Patients with an existing breast haematoma close to the target lesion.