- Pre-radiofrequency ablation (RFA) procedures: Patients undergo staging by MRI assessment to determine the size of their tumor. Patients with nonpalpable lesions must undergo placement of a metallic clip in the center of their tumor and a hook wire to guide surgical excision by intraoperative ultrasound imaging. Patients with invasive breast cancer undergo axillary lymph node dissection or sentinel lymph node biopsy (SLNB) for axillary lymph node staging. Patients with ductal carcinoma in situ proceed directly to RFA/resection since they do not require axillary staging.