Retinoblastoma is a malignant (cancerous) tumor that occurs in the eye. It arises in the part of the eye known as the retina, which is located along the back wall of the inside of the eye.
Retinoblastoma is relatively rare occurring in 1 in 18,000 births and often is diagnosed in children who are less than two years of age. It more commonly occurs in only one eye. Each child of an affected individual who has both eyes affected (bilateral retinoblastoma) has approximately a 45% chance of developing retinoblastoma themselves.