RB1 and retinoblastoma: Due to the mutation with subsequent loss of this tumor suppressor gene, various neoplasms can result including osteosarcoma, melanoma, breast, and supratentorial primitive neuroectodermal tumors.122,123 Although RB1 mutation results in classic retinoblastoma of the eye,122 osteosarcoma remains the second most common malignancy in this patient cohort.124 Screening for retinoblastomas is done in neonates with red reflex testing before discharge from the neonatal nursery.125