Retinoblastoma is a rare type of cancer found in the eye. In retinoblastoma, one or more tumors form in the retina. The retina is a layer of light-sensitive tissue that lines the back of the eye. It converts visual images into nerve impulses in the brain that allow us to see. If not treated, the tumors will continue growing. The cancer may grow along the optic nerve and reach the brain or it may travel to other parts of the body.

Cancer occurs when cells in the body (in this case retina cells) divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. Tumors can invade nearby tissue and spread to other parts of the body.

Retina of the Eye
Retina of the Eye
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During early stages of fetal development, fast-growing, immature cells called retinoblasts form. Later, these cells become retinal cells. In retinoblastoma, some of these cells quickly grow out of control. Some cases of the tumor are inherited; others are not.