Ophthalmology – Retinoblastoma

Basics

Description

Retinoblastoma (RB) is the most common primary intraocular malignancy of childhood.

It arises from the developing retina and usually presents before:

5 years of age, most commonly in the first few years of life.

It may be:

• Unilateral
• Bilateral
• Unifocal
• Multifocal
• Heritable or nonheritable

The most important presenting signs are:

• Leukocoria
• Strabismus

Any child with either finding requires:

Urgent dilated ophthalmic examination.

Key Clinical Priorities

Management follows three priorities:

1. Save life
2. Save the eye
3. Preserve useful vision

Cosmesis is secondary to these goals.

Epidemiology

Retinoblastoma occurs in approximately:

1 in 15,000–20,000 live births

Worldwide, several thousand children are diagnosed each year.

In high-resource settings, survival exceeds:

95%

when disease is confined to the eye and treated promptly.

Survival remains substantially lower in regions where diagnosis is delayed and extraocular disease is more common.

Age at Presentation

Typical patterns:

Bilateral/Heritable RB

Presents:

• Earlier
• Often during infancy
• Frequently multifocal

Unilateral/Nonheritable RB

Presents:

• Somewhat later
• Usually as a single tumor

Genetics

The fundamental genetic abnormality involves:

RB1 tumor suppressor gene

located at:

Chromosome 13q14

Knudson Two-Hit Hypothesis

Retinoblastoma provided the classic model for the:

Two-hit hypothesis

Both copies of RB1 must be functionally inactivated in a retinal precursor cell for tumor formation.

Heritable Retinoblastoma

Heritable disease involves a pathogenic germline RB1 variant.

These children have the first “hit” in all cells and require only a second somatic mutation in a retinal cell.

Features include:

• Usually bilateral disease
• Often multifocal tumors
• Earlier presentation
• Increased risk of trilateral retinoblastoma
• Increased lifelong risk of second primary malignancies

Important Modern Genetic Point

Not all unilateral retinoblastoma is nonheritable.

Approximately:

10–15% of children with apparently unilateral RB may carry a germline RB1 pathogenic variant

Therefore:

Genetic counseling and RB1 testing should be offered to essentially all affected children when available.

Nonheritable Retinoblastoma

In nonheritable disease:

• Both RB1 hits occur within the tumor
• Disease is usually unilateral and unifocal
• The mutation is not present throughout the body

However, mosaic germline disease can complicate classification.

Family History

Only a minority of patients have an obvious family history.

A negative family history does:

Not exclude heritable retinoblastoma

because germline mutations may arise de novo.

Inheritance

Heritable RB follows an:

Autosomal dominant cancer predisposition pattern

with high but incomplete penetrance depending on the variant.

An affected individual with a germline RB1 variant may transmit the variant to:

50% of offspring.

Genetic Counseling

Families should receive counseling regarding:

• Germline testing
• Recurrence risk
• Testing of parents and siblings
• Future pregnancy options
• Preimplantation genetic testing when desired
• Prenatal genetic diagnosis when appropriate

Modern counseling should support reproductive choice rather than recommend avoidance of pregnancy.

Prenatal Considerations

In a family with a known pathogenic RB1 variant, options may include:

• Prenatal genetic testing
• Preimplantation genetic testing
• Targeted fetal imaging in selected high-risk pregnancies

Fetal ultrasound alone is:

Not sufficiently sensitive to exclude retinoblastoma.

Delivery planning and prompt postnatal ophthalmic examination are more important.

Newborn Screening in High-Risk Families

Infants with:

• Known familial RB1 mutation
• A parent with heritable retinoblastoma
• A sibling with heritable disease

should undergo:

Prompt ophthalmic examination after birth

often within the first days to weeks of life depending on risk and local protocol.

13q Deletion Syndrome

Large deletions involving chromosome 13q may include:

RB1

and produce retinoblastoma associated with developmental abnormalities.

Features may include:

• Developmental delay
• Growth abnormalities
• Craniofacial dysmorphism
• Limb abnormalities

This should prompt:

Clinical genetics evaluation.

Pathophysiology

Loss of functional RB1 disrupts:

• Cell-cycle regulation
• Retinal differentiation
• Control of proliferation

allowing malignant retinal cells to proliferate.

Histology

Retinoblastoma is composed of:

• Small round blue tumor cells
• Hyperchromatic nuclei
• Scant cytoplasm
• Variable necrosis and calcification

Flexner-Wintersteiner Rosettes

A classic sign of photoreceptor differentiation is:

Flexner-Wintersteiner rosettes

These consist of tumor cells arranged around:

• A central lumen

They are characteristic but not present in every tumor.

Homer Wright Rosettes

Homer Wright-type rosettes may also be seen, reflecting:

• Neuroblastic differentiation

but are less specific.

Calcification

Retinoblastoma commonly contains:

Intratumoral calcification

This is an important imaging clue.

Growth Patterns

Retinoblastoma may grow:

Endophytically

Toward:

• Vitreous cavity

Often associated with:

• Vitreous seeds

Exophytically

Toward:

• Subretinal space

Often associated with:

• Exudative retinal detachment
• Subretinal seeds

Diffuse Infiltrating

A flat infiltrative pattern that may mimic:

• Uveitis
• Endophthalmitis
• Retinal detachment

Presenting Features

The two most common presenting signs are:

Leukocoria

White pupillary reflex

This is the most common presentation.

Strabismus

May result from:

• Macular tumor
• Reduced central vision
• Sensory visual loss

Other Presentations

Less common manifestations include:

• Red painful eye
• Secondary glaucoma
• Hyphema
• Pseudohypopyon
• Cataract
• Vitreous hemorrhage
• Orbital cellulitis-like presentation
• Proptosis in advanced extraocular disease

Leukocoria – Differential Diagnosis

Important causes include:

• Retinoblastoma
• Coats disease
• Persistent fetal vasculature
• Cataract
• Retinal detachment
• Toxocariasis
• Familial exudative vitreoretinopathy
• Retinopathy of prematurity

Because retinoblastoma is potentially fatal:

It must be excluded urgently.

Examination

Children usually require:

Examination under anesthesia (EUA)

for complete assessment.

Document:

• Number of tumors
• Tumor size
• Location
• Distance from fovea and disc
• Vitreous seeds
• Subretinal seeds
• Retinal detachment
• Anterior segment involvement

Fundus Appearance

Retinoblastoma typically appears as:

• Creamy white
• Elevated
• Retinal mass

with possible:

• Calcification
• Surface vessels
• Retinal detachment
• Vitreous/subretinal seeding

Ultrasonography

B-scan ultrasonography is highly useful.

It can demonstrate:

• Intraocular mass
• Retinal detachment
• Highly reflective calcification

Calcification strongly supports retinoblastoma in the appropriate clinical setting.

MRI

MRI of the:

Brain and orbits with contrast

is preferred for evaluating:

• Optic nerve involvement
• Extraocular extension
• Intracranial disease
• Trilateral retinoblastoma

CT

CT can demonstrate calcification but is generally:

Avoided when possible

especially in children with heritable RB because ionizing radiation may increase lifetime second-cancer risk.

Ultrasound and MRI usually provide sufficient diagnostic information.

Fundus Photography

Wide-field retinal photography helps document:

• Tumor size
• Location
• Response to treatment
• New lesions

OCT

Handheld or conventional OCT may help assess:

• Small macular lesions
• Foveal anatomy
• Tumor regression
• Treatment-related retinal damage

It is an adjunct rather than the primary diagnostic test.

Fluorescein Angiography

FA may demonstrate:

• Tumor vasculature
• Treatment effects

but is not essential for diagnosis in most cases.

Critical Diagnostic Rule

Do not perform fine-needle aspiration or intraocular biopsy of suspected retinoblastoma.

This can create:

• Extraocular tumor seeding
• Orbital spread
• Potential metastatic risk

Diagnosis is usually established clinically and with imaging.

International Classification of Retinoblastoma

The International Classification of Retinoblastoma (ICRB) groups intraocular disease by likelihood of eye salvage.

Exact definitions vary slightly between classification versions, but the practical framework is:

Group A

Small tumors away from critical structures.

Typically:

• ≤3 mm
• No vitreous or subretinal seeds

These have an excellent eye-salvage prognosis.

Group B

Larger or more posterior tumors but:

• No significant vitreous/subretinal seeding

May include:

• Macular lesions
• Juxtapapillary lesions
• Limited subretinal fluid

Group C

Localized:

• Vitreous seeds
• Subretinal seeds

close to the primary tumor.

Group D

Diffuse or extensive:

• Vitreous seeding
• Subretinal seeding

These eyes are more difficult to salvage.

Group E

Very advanced intraocular disease with features suggesting poor visual potential or increased treatment complexity.

Examples include:

• Tumor occupying much of the globe
• Neovascular glaucoma
• Massive hemorrhage
• Anterior segment involvement
• Extensive retinal detachment
• Other advanced features

Important Staging Distinction

ICRB groups A–E classify:

Intraocular disease and likelihood of eye salvage

They are not the same as:

• AJCC TNM staging
• Histopathologic metastatic-risk staging

AJCC TNM

Modern multidisciplinary care may also use:

AJCC TNM staging

to describe:

• Intraocular extent
• Regional spread
• Metastatic disease

This is particularly important in:

• Extraocular retinoblastoma
• Oncology outcome reporting

Differential Diagnosis

The major differential diagnoses include:

• Coats disease
• Persistent fetal vasculature
• Toxocariasis
• Familial exudative vitreoretinopathy
• Retinopathy of prematurity
• Retinal detachment
• Astrocytic hamartoma
• Medulloepithelioma
• Cataract

Retinoblastoma vs Coats Disease

Retinoblastoma

• White retinal mass
• Calcification common
• Vitreous/subretinal seeds possible

Coats Disease

• Telangiectatic retinal vessels
• Massive yellow lipid exudation
• Exudative retinal detachment
• No true retinal tumor

Coats disease remains one of the classic:

Pseudoretinoblastomas.

Treatment Principles

Management is individualized according to:

• Unilateral vs bilateral disease
• ICRB group
• Tumor number
• Tumor location
• Vitreous/subretinal seeds
• Visual potential
• Germline status
• Extraocular extension

Treatment should be performed in a:

Specialized retinoblastoma center.

Focal Therapy

Focal treatment is most useful for:

• Small tumors
• Residual tumors after chemotherapy
• Recurrent localized disease

Options include:

• Laser photocoagulation/thermotherapy
• Cryotherapy

Laser / Thermotherapy

Laser is often used for:

• Small posterior tumors
• Residual tumor after chemotherapy

It induces:

• Tumor vascular closure
• Thermal destruction

Cryotherapy

Cryotherapy is particularly useful for:

• Small peripheral tumors
• Anterior lesions

It is less suitable for lesions near:

• Fovea
• Optic disc

because of scar-related visual damage.

Systemic Intravenous Chemotherapy

Traditional chemoreduction uses combinations such as:

• Vincristine
• Etoposide
• Carboplatin

Systemic chemotherapy remains important particularly for:

• Bilateral disease
• Multifocal disease
• Very young infants in selected settings
• Extraocular disease
• High-risk histopathology after enucleation
• Patients where systemic coverage is advantageous

It is no longer the only major globe-salvage strategy.

Intra-Arterial Chemotherapy

Intra-arterial chemotherapy (IAC) has transformed retinoblastoma management.

A catheter is placed into the:

Ophthalmic artery

and chemotherapy is delivered directly to the affected eye.

Common agents include:

• Melphalan
• Topotecan
• Carboplatin

IAC Indications

IAC is commonly used for:

• Unilateral Group B–D disease
• Selected advanced eyes
• Recurrent disease
• Eyes poorly responsive to systemic chemotherapy

It may also be used in selected bilateral cases.

Advantages of IAC

Advantages include:

• High intraocular drug concentration
• Reduced systemic exposure
• Excellent globe salvage in many advanced eyes

IAC Complications

Potential complications include:

• Retinal vascular occlusion
• Choroidal ischemia
• Ophthalmic artery injury
• Eyelid edema
• Cranial nerve effects
• Rare systemic vascular complications

It requires an experienced:

Interventional neuroradiology/ocular oncology team.

Intravitreal Chemotherapy

Intravitreal chemotherapy is now a major treatment for:

Vitreous seeds

Common agents include:

• Melphalan
• Topotecan

Safety-Enhanced Injection Technique

Intravitreal injection in retinoblastoma requires specialized techniques to minimize tumor escape, including:

• Tumor-free injection site
• Controlled needle entry
• Cryotherapy to needle tract in some protocols

This should only be performed by:

Experienced retinoblastoma specialists.

Subretinal Chemotherapy

Highly specialized centers may also use:

• Subretinal chemotherapy

for selected persistent subretinal seeds.

This is not routine first-line therapy everywhere.

Enucleation

Enucleation remains essential for advanced eyes with poor visual potential or high-risk features.

Common indications include:

• Many Group E eyes
• Painful blind eye
• Neovascular glaucoma
• Massive tumor
• Anterior segment invasion
• Severe hemorrhage
• Failure of conservative therapy

Enucleation Principle

When enucleation is required, the optic nerve should be removed with:

As long a segment as safely possible

because histopathologic optic nerve invasion affects metastatic risk.

High-Risk Histopathology

After enucleation, pathology should specifically assess for:

• Postlaminar optic nerve invasion
• Massive choroidal invasion
• Scleral invasion
• Extrascleral extension
• Anterior segment invasion

These features may indicate need for:

Adjuvant systemic chemotherapy.

Plaque Radiotherapy

Plaque brachytherapy may be useful for:

• Localized recurrent tumors
• Residual tumors
• Selected tumors refractory to other local therapy

Its role is now more limited than historically.

External Beam Radiotherapy

External beam radiation is now:

Generally avoided whenever possible

because it increases risks of:

• Second primary malignancies
• Orbital/facial growth disturbance
• Cataract
• Radiation retinopathy
• Radiation optic neuropathy

The risk is especially important in:

Heritable RB1 mutation carriers.

Trilateral Retinoblastoma

Children with heritable retinoblastoma have increased risk of an intracranial primitive neuroectodermal tumor, most often:

• Pinealoblastoma

and less commonly a suprasellar tumor.

This combination is called:

Trilateral retinoblastoma

Brain MRI Surveillance

A brain MRI is generally obtained:

At diagnosis

particularly in:

• Bilateral disease
• Known heritable RB
• Very young children

Some centers perform serial MRI screening every several months until approximately age 5 in heritable disease, while practices vary because the optimal surveillance schedule remains debated.

Second Primary Malignancies

Patients with germline RB1 mutations have an increased lifetime risk of cancers such as:

• Osteosarcoma
• Soft-tissue sarcoma
• Melanoma
• Other epithelial and mesenchymal malignancies

Risk is especially increased after:

Ionizing radiation exposure.

Long-Term Survivorship

Heritable RB survivors require:

• Lifelong awareness of second malignancy risk
• Avoidance of unnecessary ionizing radiation
• Appropriate age- and symptom-based cancer surveillance

Routine whole-body imaging is not automatically indicated for every asymptomatic survivor.

Follow-Up of the Eyes

Children require frequent examination during and after treatment.

Early follow-up may be:

• Every few weeks
• Monthly

depending on:

• Tumor activity
• Age
• Treatment modality

Intervals are gradually extended after sustained regression.

Examination Under Anesthesia

EUA is commonly required until the child is sufficiently cooperative for complete office examination.

There is:

No rigid age cutoff

because this depends on:

• Development
• Cooperation
• Tumor complexity

Tumor Regression

Regressed tumors may become:

• Calcified
• Atrophic
• Scar-like

Different regression patterns occur depending on:

• Treatment modality
• Tumor type

A regressed scar still requires surveillance for:

• Recurrence
• New tumors in genetically susceptible children

Retinoma / Retinocytoma

A benign or spontaneously arrested RB1-related lesion called:

Retinoma/retinocytoma

may occur in some germline mutation carriers.

It can appear:

• Gray
• Calcified
• Translucent

and requires surveillance because malignant transformation can rarely occur.

Visual Prognosis

Visual outcome depends strongly on:

• Foveal involvement
• Optic disc involvement
• Tumor size
• Retinal detachment
• Treatment-related retinal injury

Small peripheral tumors may be treated with:

Excellent visual preservation.

Large macular tumors often cause permanent central visual loss despite successful tumor control.

Amblyopia

Children with unilateral or asymmetric disease are at high risk for:

Amblyopia

After tumor control, visual rehabilitation may include:

• Refractive correction
• Occlusion therapy
• Other amblyopia treatment

when safe and appropriate.

Protective Eyewear

Children with one functional eye should use:

Protective polycarbonate eyewear

to reduce trauma risk to the better-seeing eye.

Prognosis

In high-resource settings, intraocular retinoblastoma has an:

Excellent life prognosis

when detected before extraocular spread.

The major threats to survival are:

• Optic nerve extension
• Extrascleral extension
• CNS involvement
• Hematogenous metastasis

Extraocular Retinoblastoma

Extraocular disease may spread to:

• Orbit
• Brain
• Bone
• Bone marrow

This requires aggressive multidisciplinary management with:

• Systemic chemotherapy
• High-dose chemotherapy in selected cases
• Radiotherapy when necessary
• Surgical management

Poor Prognostic Features

Poorer survival is associated with:

• Delayed diagnosis
• Extraocular extension
• Postlaminar optic nerve invasion
• Massive choroidal invasion
• Scleral/extrascleral invasion
• Metastatic disease

Complications

Potential complications include:

• Visual loss
• Loss of the eye
• Amblyopia
• Cataract
• Retinal detachment
• Vitreous hemorrhage
• Glaucoma
• Radiation complications
• Chemotherapy toxicity
• Second primary malignancy
• Trilateral retinoblastoma

Ophthalmology Pearls

• Retinoblastoma is the most common primary intraocular malignancy of childhood.
• The two most common presenting signs are leukocoria and strabismus; either requires urgent dilated examination.
• The disease results from biallelic inactivation of the RB1 tumor suppressor gene on chromosome 13q14.
• Bilateral and multifocal disease should be considered heritable until proven otherwise, but even apparently unilateral RB can carry a germline RB1 mutation.
• Offer genetic counseling and RB1 testing when available because results affect family screening, future pregnancies, trilateral RB risk, and lifelong cancer surveillance.
• Retinoblastoma typically appears as a white retinal mass with calcification, often associated with retinal detachment or vitreous/subretinal seeds.
• B-scan ultrasonography is valuable for detecting calcification; MRI brain/orbits evaluates optic nerve, extraocular, and intracranial disease.
• Avoid routine CT when MRI and ultrasound are sufficient because children—especially germline RB1 carriers—should minimize unnecessary ionizing radiation.
• Never perform intraocular biopsy or fine-needle aspiration of suspected retinoblastoma because of the risk of tumor seeding.
• The ICRB A–E classification estimates intraocular disease severity and likelihood of globe salvage; it is not equivalent to metastatic staging.
• Modern treatment increasingly uses intra-arterial chemotherapy for globe salvage and intravitreal melphalan/topotecan for vitreous seeds.
• Systemic vincristine/etoposide/carboplatin remains important in bilateral, multifocal, extraocular, and selected high-risk disease.
• Enucleation remains the safest treatment for many advanced Group E eyes with poor visual potential or high-risk features.
• Histopathology after enucleation must assess for postlaminar optic nerve invasion, massive choroidal invasion, scleral and extrascleral extension, which may require adjuvant chemotherapy.
• External beam radiotherapy is now largely avoided because of second malignancy risk and orbital/facial growth abnormalities, especially in heritable disease.
• Heritable RB predisposes to trilateral retinoblastoma and lifelong second primary cancers.
• Modern management follows the priorities: save life → save eye → preserve vision.
• Long-term care includes ocular surveillance, amblyopia treatment, protective eyewear when only one eye sees well, genetic counseling, and survivorship monitoring for second malignancies.