Retinoblastoma is a neuroectodermal malignancy arising from retinal cells. It is one of the small round blue cell tumors of childhood. It is caused by a mutation of the retinoblastoma gene (RB1) located on chromosome 13q14. Children born with germline mutations of RB1 are also at risk of other primary malignancies (e.g. Osteosarcoma). The best initial step in diagnosing retinoblastoma is an immediate ophthalmoscopic examination under general anaesthesia. Biopsy of the tumor is not performed due to the risk of seeding the vitreous.
| Type | Pathogenesis | Presentation |
|---|---|---|
| Heritable Retinoblastoma | The child is born with one germline mutation of the RB1 gene. The other is acquired after birth resulting in a tumor (Two-hit hypothesis). | Presents earlier and tends to be bilateral. |
| Non-heritable Retinoblastoma | The child is born with no RB1 mutation and acquires somatic mutations of both RB1 genes after birth | Presents relatively later and tends to be unilateral. |
Accounts for about 2.5% of all childhood cancers from birth to 14 years. Affects 1 in 15,000 children. Median age of diagnosis is 15 months of age. 90% of cases are diagnosed before 5 years of age. Overall, 70-80% are unilateral. 20-30% are bilateral. Of heritable retinoblastoma, 90% of inherited mutations develop spontaneously. 10% of inherited mutations come from the parent.
- What are the other small round blue cell tumors of childhood?
- Neuroblastoma
- Hepatoblastoma
- Wilm’s tumor
- Rhabdomyosarcoma
- Ewing’s sarcoma
- Retinoblastoma
- Signs and symptoms
- Leukocoria (60%; Retinoblastoma unless proven otherwise)
- Strabismus (20%)
- Proptosis
- Ocular asymmetry
- Deterioration in vision
- Eye pain
- Glaucoma
- Orbital cellulitis
- Orbital invasion
- Hyphema (due to destruction of the anterior chamber)
- Investigations
- Ophthalmoscopic examination under general anesthesia
- The tumor appears as a whitish-pink creamy mass
- CT-scan or MRI of the orbit: to determine extra-ocular extension, infiltration, and involvement of the optic nerve
- Bilateral Bone Marrow Biopsy: for prognosis after diagnosis
- CSF cytology: for prognosis after diagnosis
- Ophthalmoscopic examination under general anesthesia
- Treatment
- External beam radiation
- Neoadjuvant chemotherapy can be used to reduce tumor bulk before radiation (using Carboplatin, Vincristine, and Etoposide)
- Chemotherapy for metastatic disease
- Enucleation if radiation and chemotherapy fail or if there is no vision in the affected eye (non-salvageable)
- External beam radiation
- 5-years survival
- 90% if confined to the orbit
- 40% if invades the optic nerve (CN II)
- Rare if there are distant metastasis
