RB1 and retinoblastoma: Germline mutations in known cancer predisposition genes (e.g., WT1 gene [chromosome 11p13] or WT2 gene [chromosome 11p15] in Wilms tumor, and RB1 gene [chromosome 13q14] in bilateral retinoblastoma) are responsible for approximately 10% of pediatric embryonal tumors, however, most cases are sporadic with no known etiology [4,5,6,7].