OBJECTIVES: To describe the technique of renal radiofrequency (RF) thermal ablation. Case report of a successful nephron-sparing surgery after failure of the RF thermal ablation of a renal adenocarcinoma in a patient with a single kidney.METHODS: A patient presenting with a renal adenocarcinoma in a single left kidney was treated by RF thermal ablation. The failure of the technique was patent on follow-up after demonstration of a central area of necrosis surrounded by a peripheral contrast enhancing area. Nephron sparing surgery was indicated as salvage procedure.RESULTS: Surgical excision of the tumor with a safety margin, without renal pedicle clamping was undertaken. Fat tissue and hemostatic synthetic material were placed in the surgical bed. Pathology report: renal adenocarcinoma with changes secondary to central necrosis. Twenty-four month postoperative follow-up: fatty renal nodule with small fibrous tracts inside in the area of the tumor. No evidence of contrast enhancing areas. Normal renal function (sCr 0.7 mg/dl, urea 24 mg/dl).CONCLUSIONS: Radiofrequency thermal ablation is a relatively new technique. Its oncological efficacy greatly depends on appropriate case selection. One of its main caveats is achieving an area of tissue ablation enough to completely destroy the tumor. When the technique fails, renal surgery (nephron sparing or not) seems to be the most recommended alternative.