Table 1.

Genetic subtypes of retinoblastoma: distribution and phenotypic correlation

	Family history	Heritability	First mutation	Second mutation	Phenotype*	Distribution
Familial	present	heritable	inherited germline	somatic	bilateral or unilateral	10%
Nonfamilial	absent	heritable	new-onset germline	somatic	bilateral or unilateral	25%
Sporadic	absent	nonheritable	somatic	somatic	unilateral	65%

^*Germline mutation can manifest as no tumor (carrier status), unilateral, or bilateral tumors. While the majority of unilateral cases (85%) are sporadic in origin, 15% of unilateral tumors can be due to underlying germline mutation.