Retinoblastomas are extremely rare withabout half of the cases being hereditary eye neoplasms in young children. They show highly proliferative, CRX-positive undifferentiated tumour cells (occasionally forming rosettes). Staging is performed according to the pTNM classification and the International Retinoblastoma Staging System (IRSS). The diagnostic basis for systemic administration of chemotherapy and/or radiation is postlaminar optic nerve invasion, massive choroidal tumour infiltration, scleral invasion or even extraocular invasion. In cases that are difficult to diagnose, immunohistochemical stains (CRX and Ki67) may be very helpful. Retinocytomas (retinomas) completely lack undifferentiated tumour cell areas, show an exclusive photoreceptor differentiation and an exceptionally low Ki67 index.
Keywords: Choroid infiltration; Eye neoplasm; Immunohistochemistry; Leukocoria.