retinoblastoma
Meaning of retinoblastoma: A childhood eye cancer usually noticed as a white glow in the pupil, and the tumor that revealed how cancer genes work.
Definition of retinoblastoma
Retinoblastoma is a cancer that arises in the retina, the light-sensing layer at the back of the eye. It almost always occurs in young children, before school age. It develops when both copies of the RB1 gene are lost or damaged in a developing retinal cell. Some children inherit one faulty copy, in which case tumors tend to appear earlier and in both eyes.
How is it usually noticed?
The most common first sign is leukocoria, a white reflection from the pupil where the red reflex should be. It is often spotted in a photograph taken with a flash, or by a parent in dim light. The second common sign is a squint, where the eyes do not point in the same direction, because a tumor blocking central vision removes the reason for that eye to align. Pain is unusual early on, and a young child cannot report reduced vision in one eye, so the outward signs matter.
What is the difference between the inherited and non-inherited forms?
| Heritable form | Non-heritable form | |
|---|---|---|
| First faulty gene copy | Present in every cell from birth | Arises in one retinal cell |
| Eyes affected | Often both | One |
| Number of tumors | Frequently several | Usually one |
| Age at diagnosis | Earlier | Later |
| Other cancers later | Raised risk | Not raised |
Why is this tumor important beyond the eye?
Retinoblastoma is where the idea of a tumor suppressor gene came from. RB1 normally acts as a brake on cell division. One working copy is enough, so a cell only loses control when both copies fail. A child with a hereditary fault already carries one broken copy in every cell of the body, so a single further event in any retinal cell is enough, which explains why tumors appear early and in more than one place. This two-step model now underpins how many other inherited cancer risks are understood. Children with the heritable form also carry a raised lifetime risk of other cancers, particularly bone tumors, which is why follow-up continues long after the retina is treated.
Used in a sentence
Examination under anesthesia confirmed bilateral retinoblastoma.
Good to know
A white pupil reflex in a young child is the classic presenting sign, and children with the heritable form carry a raised risk of separate cancers later in life.
Word origin
Where “retinoblastoma” comes from
Joins the Latin rete, meaning net, which gives retina, with the Greek blastos, a germ or sprout, and -oma, a tumor.