Patients undergo MRI-guided focused ultrasound (MRgFUS) ablation of the breast lesion using a series of pulses. Within 72 hours after MRgFUS procedure, patients undergo gadolinium-enhanced MRI to evaluate ablation borders. Within 7-10 days after MRgFUS procedure, patients undergo an ultrasound exam. Guide wires may be placed to assist in pre-surgical lesion localization. Within 10-21 days after MRgFUS procedure, patients undergo segmental resection or mastectomy.