Clinical Presentation

A 9-month-old male presents with a 4-week history of right esotropia (inward turning of the eye) and periorbital swelling.

Figure 27A

Figure 27B

Radiologic Findings

Bilateral retinoblastoma

Differential Diagnosis

• Persistent hyperplastic primary vitreous
  
• Coats’ disease
  
• Norrie’s disease
  
• Retinal astrocytic hamartomas of tuberous sclerosis
  
• Toxocara endophthalmitis
  
• Retinopathy of prematurity

Discussion

Background

Retinoblastoma is the most common intraocular tumor of childhood. It occurs in 1 in 10,000 to 15,000 live births. It is nonhereditary in 60 to 80% of cases and hereditary in the remainder. The hereditary form usually presents earlier (<2 years of age) and is frequently bilateral. Trilateral retinoblastoma represents the association of a midline intracranial tumor (usually pineoblastoma) with bilateral retinoblastoma. Retinoblastoma can also be rarely tetralateral when it is associated with a suprasellar tumor.

Etiology

The etiology of retinoblastoma includes both hereditary and nonhereditary forms. The gene responsible for retinoblastoma is localized to the 13q14 locus, which is mutated or deleted in both hereditary and nonhereditary forms. The retinoblastoma gene functions as a suppressor gene. If both alleles are suppressed or deleted, then retinoblastoma can develop. The hereditary form is autosomal dominant with a penetrance of 90% and with increased risk in trisomy 21.

Embryology

Retinoblastoma arises from retinal neuroectodermal cells.

Clinical Findings

Leucocoria (white papillary reflex) or “cat’s eye” is the most common presentation, often shown on photographs as loss of the red eye. Other presentations include:

• Strabismus
  
• Orbital inflammation
  
• Proptosis
  
• Nystagmus

Pathology

Macroscopically, retinoblastomas are noted as single or multiple white, “chalky” nodules in the retina. There are three types:

Figure 27C Axial (1) and coronal (2