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At a glance

A familial malignant ocular embryonic tumor develops in the retina due to a defect in a regulatory gene. Association with other primary malignancies is frequent. Prognosis is good.

Synonym

Rb.

History

First identified in 1500s and defined as a unique medical entity in 1809.

Incidence

Estimated at 1:14,000 to 18,000 live births. Over 90% are diagnosed before the age of 5 years. Non-white individuals present with a prevalence four times greater than whites. Bilateral cases occur in 25%.

Genetic inheritance

In general, 5 to 10% of cases are inherited, 20 to 30% are new germinal mutations, and 60 to 70% are sporadic (unilateral mainly). Heritable retinoblastoma (Rb) requires two mutations: one that is inherited in the patient’s germline and the other in the developing retina. The inherited tumors are usually bilateral, multiple, and occur at an early age. Nonheritable (acquired) Rb also requires two mutations, although both of these mutations occur in the developing retina.

Pathophysiology

The retinoblastoma gene is located at 13q14.1-q14.2 and is a negative regulator of the cell cycle through its ability to bind the transcription factor E2F and suppresses transcription of genes required for S phase. Usually develop in posterior portion of retina with multiple foci. Rb typically invades locally and grows forward into vitreous or backward into optic nerve. Rarely metastasize until very late. There is a high incidence of second primary tumors, suggesting a key role in the etiology of several other primary malignancies (osteogenic sarcoma, pinealoma, leukemia, lymphoma, and Ewing sarcoma).

Diagnosis

Clinical features and careful ophthalmologic examination. Computed tomography (CT) scan and magnetic resonance imaging (MRI) assessment of the eye and orbit is also recommended. Median age at diagnosis is 11 months for bilateral disease and 23 months for unilateral disease.

Retinoblastoma:  This 2-year-old boy with bilateral retinoblastoma shows typical leukocoria (white “cat’s eye” reflex).

Clinical aspects

Early presenting feature is leukocoria (white “cat’s eye” reflex), a yellowish-white reflex in the pupil caused by tumor behind the lens. Other common findings include diminishing or absent vision and strabismus. In more advanced disease, there may be pupillary irregularity, hyphema, and pain. Severe disease may have ptosis, raised intracranial pressure, and bone metastasis. Retinoblastoma may occur in association with other “13q-Syndromes,” which are typically characterized by growth delay, mental retardation, and minor facial anomalies. There is a high risk of other malignancies, particularly osteogenic sarcoma and other germ cell tumors. Treatment includes cryotherapy, laser ablation, local radiation, and enucleation. A novel approach is a superselective chemotherapic injection of melphalan into the ophthalmic artery using a microcatheter. Overall survival is ...

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