RB1 and retinoblastoma: Retinoblastoma is a type of intraocular cancer resulting from a mutation in both alleles of the retinoblastoma RB1 tumour suppressor gene (RB1) (Ch13q14.2) in the developing retinal progenitor cells.2 The reduction in the expression of the tumour suppressor gene eradicates the control in the cell cycle and leads to the unregulated proliferation of cells.