MYCN and retinoblastoma: Besides tumor initiation by biallelic loss of the RB1 gene, cytogenetic analysis has identified recurrent copy number variants (CNVs) in retinoblastoma tumors, leading to the proposal of several candidate driver genes other than RB1 such as KIF14, MYCN, DEK, E2F3, RBL2/p130, and NGFR [4,13,14,15,16].