Retinoblastoma

Retinoblastoma is a type of eye cancer that starts in your retina, the light-sensing layer of cells at the back of your eye. It’s the most common childhood eye cancer.

Retinoblastoma can happen in one or both eyes. About 1 in 4 cases affect both eyes. Experts suspect it happens because of a malfunction in young, developing retinal cells. Diagnosis occurs before age 3 in 4 out of 5 cases. In rare cases, adults can also develop the condition after a pause in the tumor’s early development.

Types of retinoblastoma

There are three types of retinoblastoma:

• Unilateral: This means “one-sided,” so it affects one eye only.
• Bilateral: This means “two-sided,” so it affects both eyes.
• Trilateral: This means you have cancer in three places. Each eye reflects one of those places. The third place is in the pineal gland inside your brain. (Cancer affecting that gland is called pineoblastoma.)

About 60% of retinoblastoma cases are one-sided. Bilateral and trilateral cases make up the other 40%.

How common is retinoblastoma?

Retinoblastoma is rare. There are about 3.3 cases per 1 million people under age 20. In that age group, there are a little over 300 new cases annually in the U.S. and slightly under 9,000 new cases worldwide.