Retinoblastoma

What Is Retinoblastoma?

Retinoblastoma is a rare type of eye cancer that develops in the retina, the part of the eye that detects light and color. Although this disorder can occur at any age, it usually develops in young children. Most cases of retinoblastoma occur in only one eye, but both eyes can be affected. The most common sign of this disorder is a visible whiteness in the normally black pupil (the opening through which light enters the eye). This unusual whiteness is particularly noticeable in
photographs taken with a flash, and is called "cat's eye reflex" or leukocoria.
Other signs and symptoms of retinoblastoma include crossed eyes or eyes that do not point in the same direction (strabismus); persistent eye pain, redness, or irritation; and blindness or poor vision in the affected eye. People with the hereditary form of retinoblastoma may also develop a tumor in the brain called pinealoma. Pinealoma develops in the pineal gland, which is located at the base of the skull. The presence of retinoblastoma and pinealoma together is called trilateral retinoblastoma. Later in life, people with hereditary retinoblastoma also have an increased risk of developing bone cancer (osteosarcoma), soft tissue cancers, a form of skin cancer called melanoma, and other types of cancer.

How Common Is Retinoblastoma?

Retinoblastoma affects an estimated 1 in 15,000 to 20,000 live births. This disease is diagnosed in about 250 children per year in the United States. It accounts for about 3 percent of all cancers in children younger than 15 years.


What Are the Genetic Changes Related to Retinoblastoma?

Retinoblastoma is a chromosomal condition related to chromosome 13. Variations of the RB1 gene increase the risk of developing retinoblastoma. Mutations in the RB1 gene are responsible for most cases of retinoblastoma. RB1 is a tumor suppressor gene, which means it normally keeps cells from growing and dividing too rapidly or in an uncontrolled way. Most mutations in the RB1 gene prevent it from making any functional protein, so it is unable to effectively regulate cell division. As a result, cells divide uncontrollably and form a tumor. A small percentage of retinoblastoma cases are caused by a deletion in the region of chromosome 13 that contains the RB1 gene. Geneticists refer to this region as 13q14.
Children with these chromosomal deletions may also have mental retardation, slow growth, and characteristic facial features (such as prominent eyebrows, a short nose with a broad nasal bridge, and ear abnormalities).