TCF21 and Wilms tumor: To validate TCF21 hypermethylation in CCSKs compared with other pediatric renal tumors, 8 CCSKs with available DNA from an independent validation set were also analyzed using the same primers; 7/8 of these CCSK samples showed higher methylation at these loci compared with 7 favorable histology Wilms tumors, 2 renal rhabdoid tumors, 3 congenital mesoblastic nephromas, and 2 normal kidney samples (Figure 5B).