I. To assess genomic gains and losses in high risk renal tumors, including up to 80 favorable histology Wilms tumors that relapse (RFHWT), 50 anaplastic Wilms tumors (UHWT), 15 clear cell sarcomas of the kidney (CCSK), and 40 rhabdoid tumors (RT) using a high density genetic platform to survey for recurrent copy number variations and allelic imbalances. II. To define transcription patterns within 80 RFHWT, 50 UHWT, 15 CCSK, and 40 RT using a high throughput platform for global gene expression. III. To define DNA methylation patterns within 80 RFHWT, 50 UHWT, 15 CCSK, and 40 RT using a high throughput platform. IV. To identify genetic mutations involved in the pathogenesis of Wilms tumor, and in the development of relapse and anaplasia through the study of 80 RFHWT, 50 UHWT, 15 CCSK, and 40 RT using next generation sequencing tools.