Retinoblastoma

Retinoblastoma is an aggressive tumour of the central nervous system caused by a mutation in the RB1 gene. Initial presentation typically includes leukocoria (a white pupil reflex) and strabismus with the tumour becoming increasingly calcified over time. This condition may be unilateral or bilateral.

Retinoblastoma starts within the retina and as it grows, “seeds” are produced that either adhere below the retina (subretinal seeds) or float through the vitreous (vitreous seeds), appearing as vitreous opacities ranging from fine “dust”-like seeds through to “cloud”-like seeds.

As the tumour invades locally, it can detach the retina causing inflammation and necrosis, sometimes leading to phthisis bulbi. It can also spread beyond the eye via the choroid to enter the blood supply and alternatively can enter the cerebrospinal fluid via the optic nerve.

The pre-cursor to retinoblastoma is a retinoma which is a grey translucent mass associated with chorioretinal atrophy and RPE disruption. These lesions are very rare, indicating that most retinomas undergo malignant transformation and become retinoblastoma. They may however sometimes be noted in the parents of children with retinoblastoma.

Other differential diagnoses to consider in a child with leukocoria include congenital cataract, corneal scarring, Norrie disease and ocular toxocariasis,

Dimaras, H. Corson, TW (2019) Retinoblastoma, the visible CNS tumor: a review Journal of Neuroscience Research 97(1) pp 29-41.