RF Ablation of Treatment of Metastatic Lesions in Patients Undergoing Antiangiogenic Therapy for Stage IV Renal Cell Carcinoma

* Participants will undergo a RF ablation procedure of one or more of their tumors that have not gone away while they have been undergoing antiangiogenic treatment. The RF ablation procedure will be performed in the operating room at one of the Dana-Farber/Harvard Cancer Center hospitals and will be performed under general anesthesia. * Blood will also be drawn 2-4 weeks before the procedure, at the time of teh procedure and 2-4 weeks after the procedure. * The RF ablation procedure will be performed at specified times in relation to the participants antiangiogenic treatment (sorafenib or sunitinib): a) If the participant is taking sorafenib, they will be asked to stop taking it 2-5 days prior to the RF ablation procedure; b) if the participant is taking sunitinib, they will be asked to stop taking it 4-7 days prior to the RF ablation procedure. * Participants will have an MRI or a CT scan of their tumor(s) within 2-4 weeks of the procedure and 2-4 weeks after the procedure. The MRI or CT will scan the tumor(s) to determine how much blood flow is going to them. * At the time of RF ablation, participants will have a biopsy of their tumor(s) and will receive a CT scan in the area the ablation was performed after the procedure to assess for any bleeding. They will also be monitored for 4 hours after the RF ablation procedure.