Retinoblastoma is a malignant primitive neuroectodermal tumor (PNET) arising in the retina. It is the commonest intraocular tumor of childhood; the average age at presentation is 18 months. CT demonstrates a contrast-enhancing retrolental mass that is usually calcified. A dense vitreous due to hemorrhage is common. 40% are bilateral and these are often synchronous. Direct spread may occur into the orbit or occur along the optic nerve into the brain. Distant metastases are less common. Approximately 60% of cases are sporadic and 40% are inherited, the latter usually due to a germline mutation in the RB tumor suppressor gene. Children with this mutation are at increased risk of developing “trilateral retinoblastoma” (bilateral retinoblastomas and pineoblastoma) and osteosarcoma.
Case courtesy of Dr Donna D'Souza.