Retinoblastoma in Children
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Direct answer
A white pupillary reflex (leucocoria) in an infant, often first seen in a flash photograph, is retinoblastoma until excluded: the commonest intraocular malignancy of childhood, from biallelic inactivation of the RB1 tumour suppressor gene at 13q14 — the foundation of Knudson's two-hit hypothesis. Roughly 40% of cases are heritable, presenting younger and bilaterally, carrying a lifelong risk of second primaries such as osteosarcoma and of trilateral disease with a pineal tumour. Diagnosis is examination under anaesthesia with funduscopy, ultrasonographic calcification and magnetic resonance staging; biopsy is never performed (risk of spread). Treatment follows the hierarchy of saving the child, then the eye, then vision: enucleation for advanced eyes, chemo-reduction with focal therapy for salvageable eyes, intravitreal chemotherapy for seeding.
What you must remember
- Presentation order: leucocoria (commonest), strabismus (second), painful red eye with glaucoma, and proptosis — late, and still the presenting stage in many Indian children.
- Two-hit genetics: heritable disease (germline RB1 mutation, every cell vulnerable) is bilateral or multifocal in most, earlier in onset, transmissible to half of offspring; non-heritable disease is unilateral, unifocal and not transmissible — the exam's recurring genetic counselling sum.
- Diagnostic discipline: fundus examination under anaesthesia, ultrasonography demonstrating calcification (the signature), magnetic resonance imaging of orbits and brain for optic nerve and pineal assessment; no biopsy, ever.
- Grouping: the International Intraocular Retinoblastoma Classification grades eyes A to E — from small tumour away from critical structures (A) to enormous with destruction, glaucoma or haemorrhage (E), the enucleation group.
- Treatment ladder: Group E eyes undergo enucleation with histopathology of the margin; Groups B-D receive chemo-reduction (carboplatin, vincristine, etoposide) with focal consolidation (laser, cryotherapy), intra-arterial chemotherapy, plaque brachytherapy, and intravitreal melphalan for seeding.
- External beam radiation: largely abandoned for intraocular disease in heritable cases because of second-cancer risk and facial deformity, though it retains a role in extraocular disease.
- Indian burden: India contributes a large share of global retinoblastoma, commonly quoted near a fifth; advanced extraocular presentation remains commoner than in high-income series.
Working through a white reflex, step by step
A fifteen-month-old is brought for a white glow in the left eye seen in photographs; the right eye appears normal. Step one is the red-reflex examination of both eyes in a dim room — asymmetry or absence confirms the finding, and both eyes are always examined because heritable disease is bilateral. Step two is urgent referral, not observation. Step three is the examination under anaesthesia: a cream-white retinal mass with calcific gleam, mapped and measured, with ultrasonography showing intraocular calcification and magnetic resonance imaging excluding optic nerve invasion, extraocular extension and a pineal lesion. Step four assigns the group — a unilateral Group D eye with vitreous seeding begins chemo-reduction with focal therapy, while a blind, painful Group E eye is enucleated with histopathology of the optic nerve margin deciding adjuvant chemotherapy. Step five is the family: siblings screened, genetic testing offered, and a clear statement that a heritable-affected parent carries a 50% transmission risk.
Follow-up examinations under anaesthesia continue at decreasing intervals for years, since new tumours arise in heritable disease and treated eyes need consolidation checks.
Where students slip
The diagnostic errors are scored hardest: performing or requesting a fine-needle biopsy (never — risk of spread), or accepting a single normal eye examination without dilation, missing a small posterior pole tumour. The genetic slips are two: assigning 50% recurrence risk to non-heritable unilateral disease (sporadic unilateral children without a germline mutation carry near-population risk), and forgetting second malignancy surveillance in germline survivors — osteosarcoma after radiation being the classic pairing. The staging slip is under-calling advanced Indian disease: a proptotic child has extraocular retinoblastoma and needs systemic chemotherapy, not eye-salvage discussion; the hierarchy — child, eye, vision — exists precisely to order these choices.
Frequently asked questions
What is the commonest presentation of retinoblastoma?
Leucocoria — a white pupillary reflex, frequently noticed first in flash photographs — followed by strabismus; a painful glaucomatous eye or proptosis indicates advanced disease.
Why is biopsy never performed in suspected retinoblastoma?
Because intraocular biopsy risks seeding tumour cells outside the eye; diagnosis rests on examination under anaesthesia with ultrasonographic calcification and magnetic resonance staging.
What distinguishes heritable from non-heritable retinoblastoma?
Heritable disease carries a germline RB1 mutation, presents younger, usually bilaterally or multifocally, is transmissible to half of offspring, and predisposes to second cancers such as osteosarcoma.
When is enucleation indicated?
For Group E eyes — advanced intraocular disease with destruction, glaucoma or haemorrhage, or any eye with no visual potential — with histopathology guiding adjuvant therapy.
What is trilateral retinoblastoma?
The combination of bilateral heritable retinoblastoma with a pineal or suprasellar primitive neuroectodermal tumour, which is why brain imaging belongs to staging and surveillance.