Onset of Retinoblastoma
Retinoblastoma typically occurs in early childhood, with risks beginning in early infancy and approximately 80% of cases diagnosed before age 4 years, with a median age at diagnosis of 2 years. 1, 2
Age Distribution and Timing
Hereditary retinoblastoma risks begin in early infancy, requiring ophthalmologic examination promptly after birth (ideally within 24 hours) for at-risk infants to maximize visual outcomes through early tumor detection 1
Bilateral retinoblastoma presents earlier than unilateral disease, with bilateral tumors typically appearing at 18-24 months compared to unilateral cases at approximately 36 months 3
Over 90% of retinoblastoma cases present before age 5 years, making this the critical surveillance window 4
Neonatal retinoblastoma can be diagnosed in the first month of life, with family history being the most common reason for detection (67% of cases) rather than leukocoria (13%) in this age group 5
Age-Related Clinical Patterns
Young age at onset is a predictor of hereditary disease in children with unilateral unifocal retinoblastoma, along with macular tumor location 1
Children diagnosed at ≤12 months have a higher proportion of RB1 gene pathogenic variants compared to those diagnosed after 12 months (P=0.034) 6
Retinoblastoma in children older than 5 years is uncommon but does occur, representing only 16 out of 453 cases (3.5%) in one series, with a median age at diagnosis of 73.7 months (range 65-144 months) 2
Bilateral or trilateral retinoblastoma in children aged 3-5 years warrants RB1 gene testing even without family history, as there remains a significant proportion of pathogenic variants in this age group 6
Clinical Implications for Surveillance
The yearly incidence of retinoblastoma in children under 15 years is 0.00036%-0.00041%, making it a rare but critical diagnosis to identify early 1
Diagnosis is often delayed in older children (>5 years) due to low clinical suspicion at this age, with a mean time between first symptoms and diagnosis of 9.6 months 2
Adult-onset retinoblastoma (>20 years) is extremely rare, with only 45 cases reported in the literature as of 2016, though increasing awareness has led to more recent reports 7
Common Pitfalls
Do not dismiss the possibility of retinoblastoma based solely on age, as cases can occur beyond the typical 0-5 year window, though with decreasing frequency 2, 7
Family history may be absent in hereditary cases due to de novo germline RB1 pathogenic variants or variants with reduced penetrance, so germline testing should be performed for all children with retinoblastoma regardless of laterality or family history 1
Delayed diagnosis in older children leads to more advanced disease at presentation, with most cases in children >5 years diagnosed at advanced stages (Reese V or extraocular disease) 2