Retinoblastoma

Retinoblastoma is a malignant tumor arising from retinal cells, usually in young children. It commonly develops when both copies of the RB1 tumor-suppressor gene are inactivated.

RB1: RB1 is a tumor-suppressor gene whose protein restrains cell-cycle progression. Inactivation of both copies is the central genetic event in most retinoblastomas.
Leukocoria: Leukocoria is an abnormal white reflection from the pupil, often visible in photographs or under examination. It is a common presenting sign that can prompt evaluation for retinoblastoma.
Heritable retinoblastoma: Heritable retinoblastoma results from a germline pathogenic variant in one copy of RB1. Affected children can develop tumors in both eyes and remain at risk for later cancers.
Sporadic retinoblastoma: Sporadic retinoblastoma arises after RB1 inactivation occurs in retinal cells rather than being inherited in the germline. It typically affects one eye and carries different familial implications from heritable disease.
Two-hit hypothesis: The two-hit hypothesis holds that tumor-suppressor genes must lose function in both copies for many cancers to develop. It explains why inherited RB1 variants predispose children to multiple retinal tumors.
Retinal examination: A retinal examination uses direct or indirect visualization to assess the back of the eye. Examination under anesthesia can reveal tumors in young children who cannot cooperate.
Second primary cancer: A second primary cancer is a new, independent malignancy arising after an earlier cancer. Survivors with heritable RB1 variants face elevated risks, especially after radiotherapy.
Bilateral retinoblastoma: Bilateral retinoblastoma is retinoblastoma affecting both eyes. It is strongly associated with heritable RB1 variants, unlike most unilateral cases.
Retinal progenitor cell: A retinal progenitor cell is an immature cell capable of producing specialized retinal cell types. Retinoblastoma is thought to arise when susceptible developing retinal cells lose RB1 function.
Intra-arterial chemotherapy: Intra-arterial chemotherapy delivers anticancer drugs through a catheter into an artery supplying a tumor. It can concentrate treatment in the affected eye while limiting systemic exposure.

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