It has been reported that numerous genes (function as tumor suppressors) were hypermethylated in primary RCC, such as CDH1, APAF1, PCDH17, SFRP1, SFRP4 and TCF21. However, these genes are not methylated or rarely methylated in matched normal renal tissues [27–29]. This evidence concerns the gene SFRP4 and renal cell carcinoma.