Retinoblastoma is a rare type of eye cancer that begins in the retina, the sensitive lining on the inside of the eye. It most commonly affects young children, but can rarely occur in adults. The retina is made up of nerve tissue that senses light as it comes through the front of the eye. Retinoblastoma cells can invade further into the eye and nearby structures, and can also spread (metastasize) to other areas of the body, including the brain and spine.

The chain of events inside cells that leads to retinoblastoma is complex, but it almost always starts with a change (mutation) in the RB1 gene. The normal RB1 gene helps keep cells from growing out of control, but a change in the gene stops it from working like it should. Depending on when and where the change in the RB1 gene occurs, it can result in two different types of retinoblastoma. In about one out of three children with retinoblastoma, the abnormality in the RB1 gene is congenital (present at birth) and is in all the cells of the body, including all of the cells of both retinas. This is known as a germline mutation.

The diagnosis of retinoblastoma is made when a doctor finds a tumor in the eye by using an ophthalmoscope (an instrument that helps doctors to look inside the eye) . As with retinoblastoma, the diagnosis is usually made based on where the tumor is inside the eye and how it looks. A biopsy (removing cells from the tumor to be looked at under a microscope) to confirm the diagnosis is almost never done because it might harm the eye or risk spreading the cancer outside of the eye.

The treatment for retinoblastoma depends on the size and location of the tumor and whether the tumor has spread. Several types ...