Regarding Retinoblastoma all are true EXCEPT:

25% Bilateral REF: Khurana 4thed p. 281, Page 1043 RETINOBLASTOMA It is the most common primary intraocular malignancy of childhood in all racial groups. Affects infants and children. Retinoblastoma affects boys and girls with equal frequency and has no known racial predilection. The most common presenting manifestation of retinoblastoma is a white glow in the pupil (leukokoria) Unilateral (60-70%) or bilateral (30-40%) ocular involvement; most unilateral cases are unifocal, and most bilateral cases are multifocal in both eyes. Germinal (heritable, 40%) and somatic (nonheritable, 60%) forms. Inherited as an autosomal dominant trait. A gene responsible for the childhood eye tumor retinoblastoma was identified in 1986 on chromosome 13q14. Among individuals who inherit a mutant copy of the retinoblastoma gene, 90% sustain a second hit to the remaining normal copy of the gene and develop a tumor. Approximately 10% of individuals who inherit a mutant copy of the gene do not sustain a second mutation and do not develop a tumor.