Eye, Retinoblastoma

Retinoblastoma is the most common primary intraocular malignancy of childhood. The tumour is of neuronal origin and results from the loss or inactivation of both alleles of the RB gene. Patients with germline RB mutations may present with bilateral retinoblastomas or “trilateral” retinoblastoma (associated with pineoblastoma).

Microscopically, retinoblastomas are a small round blue cell tumour and may show varying degrees of differentiation. As seen in this case, differentiated areas demonstrate characteristic Flexner-Wintersteiner rosettes (tumour cells surrounding a central lumen) and Homer Wright rosettes (tumour cells surrounding a less defined lumen). Invasion of the optic nerve, choroidal invasion, and/or extra-ocular extension are poor prognostic features.