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Cancer Explained

Disponible en español: Afecciones precancerosas

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Precancerous Conditions

A plain-language explanation of precancerous conditions — changes in cells that are not yet cancer but could become cancer. Based on the National Cancer Institute.

NCI source

Last reviewed: 2026-07-07

The short answer

A precancerous condition is a change in cells that is not cancer but is more likely to become cancer over time. Finding and treating these changes early — through screening — can prevent some cancers from developing.

  • A precancerous condition is a cell change that is not cancer but could become cancer.

  • Examples include colon polyps, cervical changes, and Barrett's esophagus.

  • Not all precancerous changes become cancer, and some go away on their own.

  • Screening can find and remove these changes before cancer develops.

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The full explanation.

The simple version

A precancerous condition is a change in cells that is not cancer, but is more likely than normal cells to become cancer over time. Finding these changes early is a big part of why cancer screening works.

Common examples

Precancerous changes include:

  • Polyps in the colon, which can become colorectal cancer
  • Abnormal cervical cells found on a Pap test
  • Barrett's esophagus, linked to esophageal cancer
  • Certain skin or mouth changes

Not a certainty

Having a precancerous change does not mean you will get cancer. Many never progress, and some go away on their own. But because some do become cancer, doctors often watch or treat them.

A precancerous change may become cancer — but many never do.

Why screening helps

Screening tests like colonoscopy and the Pap test can find precancerous changes and remove or treat them before cancer develops. This is one of the main ways screening prevents cancer, not just finds it early.

Words to know

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Common questions

What is a precancerous condition?

It is a change in cells that is not cancer but is more likely than normal cells to turn into cancer over time. It is sometimes called a precancerous or premalignant change.

What are some examples?

Examples include polyps in the colon, abnormal cervical cells found on a Pap test, Barrett's esophagus, and certain skin changes. Each raises the risk of a specific cancer.

Does a precancerous change always become cancer?

No. Many precancerous changes never become cancer, and some go away on their own. But because some do progress, they are often watched or treated.

How are they found and handled?

Screening tests, like colonoscopy or a Pap test, can find precancerous changes. Removing or treating them early can prevent some cancers from ever developing.

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Precancerous Conditions