Classification of retinoblastoma

Retinoblastoma can be:

• familial or sporadic
  • around 94% of newly diagnosed retinoblatomas are sporadic (without a family history of the disease)
  • the remaining 6% are familial
• bilateral or unilateral
  • the disease is unilateral in 70-75% of patients and bilateral in the remaining
• heritable or non heritable
  • around 40-50% of cases are hereditary
    • results from germline mutations which can be either a new-onset germline mutation (negative family history) or from a mutation transmitted as an autosomal trait (1,2)
    • typically inherited in an autosomal dominant pattern (2)
    • can manifest as either unilateral or bilateral disease (1)
  • 50-60% are non hereditary (1)
    • occurs secondary to somatic mutations (2)
    • the tumour always manifests as unilateral disease (1)

All three classification schemes are interrelated (1).

• bilateral and familial retinoblastomas results from a germline mutation and are thus considered heritable tumours (3)
• unilateral sporadic disease is usually not considered as a heritable condition
  • around 10-15% of unilateral sporadic cases have a germline mutation while the remaining are caused by somatic mutations (1,3)

Reference:

• (1) McDaid C et al. Systematic review of effectiveness of different treatments for childhood retinoblastoma. Health Technol Assess. 2005;9(48):iii, ix-x, 1-145.
• (2) Melamud A, Palekar R, Singh A. Retinoblastoma. Am Fam Physician. 2006;73(6):1039-44.
• (3) Shields CL, Shields JA. Diagnosis and management of retinoblastoma. Cancer Control. 2004;11(5):317-27.