Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Retinoblastoma

What Is It?

Retinoblastoma, a cancerous tumor of the retina in the eye, is a rare form of cancer that affects children, most commonly before age 5. The retina is the nerve tissue at the back of the eye that senses light and sends images to the brain, which interprets these images. Retinoblastoma, though rare, is the most common tumor of the eye in childhood years.

The disease affects about one in every 15,000 to 20,000 children. According to the American Cancer Society, retinoblastoma is responsible for 5% of childhood blindness. However, with treatment, 85% of children with retinoblastoma maintain their sight.

Approximately 40% of retinoblastoma cases are hereditary. The hereditary form usually affects younger children (under age 2) and can affect one eye (unilateral) or both eyes (bilateral). However, unilateral retinoblastoma is usually not hereditary and occurs most commonly in older children. All cases of bilateral retinoblastoma are hereditary. Bilateral retinoblastomas can also be associated with a tumor of a small gland in the brain, called the pineal gland tumor.

Children who develop retinoblastoma are more likely to develop other types of cancer later in life. The risk is higher in children with the hereditary type and children who have received radiation therapy or certain types of chemotherapy. Children who develop retinoblastoma in one eye have an increased risk of developing retinoblastoma in the other eye and require frequent eye exams even after treatment. Doctors also recommend that all children with retinoblastoma continue to be checked for other cancers regularly for the rest of their lives. A great proportion of the second cancers that develop in long-term survivors of childhood retinoblastoma can be attributed to the use of radiation therapy treatments use to treat the original retinoblastoma.

Retinoblastoma has received a great deal of study and attention by physicians and scientists involved in the genetics of cancer. There is a specific gene involved in the development of retinoblastoma, hence the high likelihood of inheriting the disease. In the hereditary form of the disease, all of the affected patient's cells have one genetic mutation, which in and of itself is unable to cause the disease to occur. If the patient then develops a second mutation in a susceptible cell in the lining of the eye (the retina), the cancer can develop, and if it does, it is usually bilateral. In the nonhereditary form or sporadic form, both genetic defects occur randomly in the individual and generally result in the formation of a unilateral (only one eye affected) disease.

The heritable form (and the responsible gene) of retinoblastoma can also be associated with several other types of cancer, including cancers of the soft tissues or bone (so called sarcomas) or a very virulent type of skin cancer called malignant melanoma.