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Small growths of colon tissue that protrude into the colonic or rectal lumen. They are usually asymptomatic, but sometimes cause visible rectal bleeding, and, rarely, other symptoms. Polyps may occur individually but it is common for a person to have multiple polyps. They occur more commonly in later life, and hereditary and dietary (lifestyle) factors may play a part.

Polyps may become cancerous and are generally defined as 2 main types:

  • hyperplastic: a type of polyp that has a low risk, if any, of developing into a cancer. However, people with multiple hyperplastic polyps are associated with an increased risk of bowel cancer.
  • adenoma (adenomatous): a polyp that has a higher chance of becoming cancerous, as it contains molecular characteristics that are common with adenocarcinoma.
Polyp number, size and microscopic features may also predict the likelihood of a polyp becoming cancerous, with larger and flatter (non-stalked) polyps having the higher risk. During a colonoscopy polyps are removed, thus lowering the risk of bowel cancer developing in the person.


AIHW 2013. National Bowel Cancer Screening Program Monitoring report July 2011–June 2012. Cat. no. CAN 71. Canberra: AIHW.

This content Based on Australian Institute of Health and Welfare material. Attribution provided as required under the AIHW CC-BY licence.

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