Radiotherapy is known to increase the risk of SMNs [35]; 61.11% of the patients in our review were exposed to some radiotherapy, which is a frequent treatment that increases this risk for patients with RB for SMNs considering the intrinsic risk of SMNs with patients with hereditary RB and the increased risk with this de novo mutation in the RB1 gene presented in our case. The gene discussed is RB1; the disease is retinoblastoma.