What is retinoblastoma?

Last medical review:

Retinoblastoma starts in the cells of the retina in the eye. A cancerous (malignant) tumour is a group of cancer cells that can grow into nearby tissue and destroy it. The tumour can also spread (metastasize) to other parts of the body.

The retina is located at the back of the eyeball. The eye is the organ that lets us see. The retina is made up of special cells that are sensitive to light and colour. When we look at something, light enters the eye and these cells help send signals to the brain to create the image of what we are looking at.

Diagram of the structure of the eyeball
Diagram of the structure of the eyeball

Retinoblastoma is usually found in children younger than the age of 2.

When a fetus (baby) is growing in the uterus, the eyes are one of the first organs to develop. In the early stages of development, the eyes have cells called retinoblasts that grow and divide quickly to create the retina. At a certain point, the retinoblasts stop growing and dividing and they mature into retinal cells.

But in rare cases, changes to retinoblasts can cause retinoblastoma. Very rarely, the retinoblasts continue to grow out of control instead of maturing into retinal cells. These retinoblasts can develop mutations in the retinoblastoma 1 (RB1) gene and form a cancerous tumour called retinoblastoma. The normal RB1 gene helps keep cells from growing out of control, but if there is a mutation in this gene, the retinoblasts don't mature and develop as they should. There are 2 copies of the RB1 gene in every cell. There must be a mutation in both copies of the RB1 gene in a retinoblast for a retinoblastoma tumour to develop.

Expert review and references

  • Stephanie Kletke, MD, FRCSC
  • American Cancer Society. Retinoblastoma. 2018. https://www.cancer.org/.
  • Cancer Research UK. Retinoblastoma. 2024. https://www.cancerresearchuk.org/.
  • Choudhary MM, Singh AD. Ophthalmic cancers. Raghavan D, Ahluwalia MS, Blanke CD, et al, eds.. Textbook of Uncommon Cancers. 5th ed. Hoboken, NJ: Wiley Blackwell; 2017: Kindle version chapter 68 https://read.amazon.ca/?asin=B06XKD44V3&_encoding=UTF8&ref=dbs_p_ebk_r00_pbcb_rnvc00.
  • Leahey AM, Gombos DS, Chevez-Barrios P. Retinoblastoma. Blaney SM, Adamson PC, Helman LJ (eds.). Pizzo and Pollack's Pediatric Oncology. 8th ed. Wolters Kluwer; 2021: Kindle version, [chapter 32] https://read.amazon.ca/?asin=B08DVWZNVP&language=en-CA.
  • Mallipatna AC, Gallie BL, Chévez-Barrios P, et al. Retinoblastoma. Amin, MB (ed.). AJCC Cancer Staging Manual. 8th ed. Chicago, IL: American College of Surgeons; 2017: 68:827–839.
  • PDQ® Pediatric Treatment Editorial Board. Retinoblastoma Treatment (PDQ®) – Health Professional Version. Bethesda, MD: National Cancer Institute; 2024. https://www.cancer.gov/.
  • PDQ® Pediatric Treatment Editorial Board. Retinoblastoma Treatment (PDQ®) – Patient Version. Bethesda, MD: National Cancer Institute; 2021. https://www.cancer.gov/.

The eyes

Retinoblastoma starts in the cells of the retina in the eye. The eyes are a part of the central nervous system and work with the brain to let us see.

Types of retinoblastoma

Non-heritable retinoblastoma and heritable retinoblastoma are 2 main types of retinoblastoma that occur in children.

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