Table 5.

Pretest Empiric Risks for Development of Retinoblastoma in Offspring of a Proband Based on Family History and Retinoblastoma Presentation in the Proband

Family HistoryRetinoblastoma Presentation in ProbandRisk to Offspring of the Proband
UnilateralBilateral
MultifocalUnifocal
Positive+Risk to offspring is variable. 1
+Risk to offspring is 50%.
Negative+The presence of a germline RB1 cancer-predisposing variant is assumed (H1) & the risk to each offspring of inheriting the pathogenic variant is 50%. 2
+Risk to offspring is 6%-50%. 3
+Risk to offspring is 6%, reflecting the possibility that the proband has mosaicism for a pathogenic variant or a germline RB1 pathogenic variant assoc w/milder phenotypic expression. 4
1.

In families with unilateral retinoblastoma, penetrance varies widely.

2.
3.
4.

In families with "familial low-penetrance retinoblastoma," the risk for tumor development in persons with the low-penetrance RB1 allele is lower than the 95% observed with highly penetrant RB1 "null" alleles.

From: Retinoblastoma

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