3. Intraocular tumours: Retina 2

Overview of Retinal Tumours

  • Topic: Retinoblastoma and Astrocytic Hamartoma

Retinoblastoma

Definition and Origin

  • A malignant congenital tumour derived from neural elements of the embryonic retina.

Epidemiology

  • Diagnosis Age: Affected cells are only present in the first few years of life; most cases diagnosed prior to age 3.

  • Incidence Rate: Rare, affecting 1 in 18,000 live births.

  • Prevalence: Represents 3% of all childhood cancers.

  • Significance: Most common primary intraocular malignancy in childhood.

  • Hereditary Nature: Bilateral cases generally hereditary, linked to a mutation of the RPE1 gene on chromosome 13.

  • Inheritance Pattern: Inherited in approximately 40% of cases in an autosomal dominant (AD) manner with variable penetrance.

Clinical Presentation

  • Timing of Presentation:

    • Presents within the first year if bilateral.

    • Presents around 2 years of age if unilateral.

  • Common Signs:

    • Leukocoria: 60% of cases presenting sign.

    • Strabismus: Presenting sign in 20% of cases.

  • Additional Presentations:

    • Secondary glaucoma.

    • Diffuse retinoblastoma may invade anterior segment leading to red eye from tumour-induced uveitis.

    • Iris nodules may be associated with pseudo-hypopyon.

    • Orbital inflammation; orbital invasion may cause proptosis.

Differential Diagnosis for Leukocoria

  • Possible Causes:

    • Toxocara granuloma.

    • Persistent hyperplastic primary vitreous.

    • Coats disease.

    • Retinopathy of prematurity.

    • Congenital cataract.

    • Note: Any child presenting with strabismus must have a dilated examination to rule out retinoblastoma.

Tumour Characteristics

  • Appearance of Early Tumours:

    • May appear as flat or round white lesions.

    • Intraretinal tumour often presents as homogenous, dome-shaped white lesions; can become irregular and may show white calcific flecks.

    • Endophytic tumours project into the vitreous as white masses.

    • Exophytic tumours present as subretinal, multi-lobed white masses.

      • Possible Overlying retinal detachment (RD).

Growth Patterns of Tumours

  • Types of Growth:

    • Endophytic: Growth into vitreous.

    • Exophytic: Growth into subretinal space leading to retinal detachment.

    • Optic nerve invasion: Tumour may spread along optic nerve to the subarachnoid space of the brain.

    • Diffuse infiltration of retina.

    • Metastatic spread: Can extend to regional lymph nodes, lungs, brain, and bones.

Risk Factors for Metastatic Disease

  • Increased Risk:

    • Advanced tumour stage.

    • Retrolaminar optic nerve involvement.

    • Choroidal invasion.

    • Anterior chamber (AC) involvement.

    • Orbital spread.

    • Repeat occurrences after treatment.

Management and Treatment

  • Importance of Early Diagnosis: Correlates with a higher chance of preserving vision, salvaging the eye, and preserving life.

  • Treatment Options Include:

    • Laser treatment for small tumours.

    • Chemotherapy in conjunction with local treatments.

    • Use of radioactive plaques.

    • Enucleation as a common treatment for large tumours.

  • Mortality Rate: Overall mortality rate is about 10%; this escalates to 65% in patients with optic nerve involvement beyond the point of surgical transection.

  • Genetic counselling is necessary, and screening for at-risk family members is recommended.

    • Patients with heritable retinoblastoma also have a predisposition to non-ocular cancers such as pineoblastoma, osteosarcoma, soft tissue sarcoma, and melanoma.

Astrocytic Hamartoma (Astrocytoma)

Definition and Nature

  • Composition: Hamartomas consist of tissue that is normal for the location but is malformed or mal-arranged.

  • Origin: Astrocytic hamartomas arise from astrocytes in the optic nerve head (ONH) and nerve fibre layer (NFL).

  • Characteristics:

    • May be bilateral and show multiple lesions in the same eye.

    • Can occur anywhere in the retina but predominantly found in ONH.

  • Related Conditions:

    • Often associated with Tuberous sclerosis and neurofibromatosis.

    • May also occur as isolated findings in otherwise healthy patients.

  • Appearance:

    • Can present as flat, dirty-white translucent oval lesions.

    • May also appear as calcified, whitish-yellow, multiple lobed, mulberry-like lesions.

      • fish egg appearance.

  • Size Range: From half-disc diameter (DD) to several DD in size.

  • Symptoms: Generally asymptomatic, though visual acuity (VA) may be decreased, and possible visual field defects due to compression of axons on ONH.

  • Prognosis: Benign (non-life-threatening). Won’t metastasise. Can lead to changes in VF due to compression of nerve fibres.

Cavernous Retinal Haemangioma

  • Definition: A rare, congenital vascular mass in the retina.

  • Characteristics:

    • Typically unilateral.

    • Commonly diagnosed in the 2nd to 3rd decades of life, often presenting with vitreous haemorrhage.

    • Generally a coincidental finding.

    • Referral needed - can cause bleeding.

  • Appearance: Clusters of aneurysm-like formations resembling a bunch of grapes in the peripheral retina.