Retinoblastoma is a form of cancer that develops on the retina. The retina is the structure at the back of the eye that senses light. It sends images to the brain which interprets them. In short, the retina allows us to see.
Although rare, retinoblastoma is the most common eye tumor in children. In most cases, it affects youngsters before age 5. It causes 5% of childhood blindness. But with treatment, the vast majority of patients maintain their sight.
About 40% of retinoblastoma cases are hereditary. This form of the disease usually affects children under age 2. It can affect one eye (unilateral) or both (bilateral).
All cases of bilateral retinoblastoma are hereditary. These cases can be associated with a tumor in the brain's pineal gland. Unilateral retinoblastoma is usually not hereditary. It generally occurs in older children.
Children with retinoblastoma are more likely to develop other types of cancer later in life. The risk is higher in children with the hereditary type. Children treated with radiation therapy or certain types of chemotherapy also have a higher risk. Children who develop retinoblastoma in one eye have an increased risk of developing it in the other eye. They need frequent eye exams—even after treatment.
Doctors recommend that children with retinoblastoma get checked regularly for other cancers throughout their lives. Many of the second cancers that develop in long-term survivors of childhood retinoblastoma are caused by the radiation therapy used to treat the original cancer.
A specific gene leads to the development of retinoblastoma. In the hereditary form of the disease, all of the patient's cells have a mutation, or change, in this gene. On its own, this single mutation doesn't cause the disease. But if the patient develops a second mutation in a retina cell, the cancer can develop. If it does, both eyes are usually affected.
In the nonhereditary, or sporadic, form, both mutations occur by chance. It usually affects one eye.
The hereditary form of the disease—and the gene that causes it—can be associated with other types of cancer. These include cancers of the soft tissues or bone and an aggressive form of skin cancer.