While a paediatric cancer predisposing tumour suppressor gene commonly mutated in retinoblastoma and to a lesser extent osteosarcoma63, and less common as an adult cancer predisposing gene64, Retinoblastoma transcriptional corepressor 1 (RB1) is recognised as one of five most prevalent somatically mutated genes in metastatic cancers65, with RB1 loss in prostate tumours associated with poor patient outcomes66. The gene discussed is RB1; the disease is retinoblastoma.