What is Retinoblastoma? The retinoblastoma gene is a type of gene known as a "tumor suppressor gene." Tumor suppressor genes act as a "brake" on cell division. The retinoblastoma gene is present in all cells of the body. If an unwanted mutation forms in one of the cells of the body, the retinoblastoma protein (also known as pRB) acts as a brake to prevent that mutant cell from dividing. However, if the retinoblastoma gene is damaged (mutated), a defective pRB may be produced and the cell can then divide unchecked, leading to cancer. Retinoblastoma arises from the retina of the eye; it affects one eye in approximately 75% of cases, and both eyes in 25% of cases. It causes a tumor to form within the eye, which can then grow and destroy the internal structures of the eye. It can also spread to other areas such as the eye socket, brain, lungs, and bones. However, ... read more on Retinoblastoma: The Basics