Retinoblastoma is a malignant primitive neuroectodermal tumour (PNET) arising in the retina. It is the commonest intraocular tumour 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 haemorrhage 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 tumour suppressor gene. Children with this mutation are at increased risk of developing “trilateral retinoblastoma” (bilateral retinoblastomas and pineoblastoma) and osteosarcoma.
References:
1. Dahnert W. Radiology Review Manual, 5th edition. Lippincott, Williams and Wilkins 2003
2. Kumar V. et al Robbins and Cotran Pathologic Basis of Disease, 7th edition, Elsevier Saunders 2005
Credit: Dr Donna D’Souza
