In previous studies, the investigators tried to use CA9 to improve the differential diagnosis of kidney tumors using tumor biopsy or fine needle aspiration. More recently, the investigators have developed the ELISA and quantitative reat time polymerase chain reaction (RT-PCR) to study the CA9 protein and CA9 mRNA in the serum of patients with non-metastatic kidney cancer. The investigators have thus shown that CA9 was overexpressed prior to surgery and that this expression disappeared after tumor ablation.