What is cancer screening, and why is it done?

Cancer screening means checking for cancer, or for abnormal cells that may become cancer, in people who have no symptoms, according to the U.S. National Cancer Institute (NCI). It is done to look for cancer early, before symptoms appear, when it may be easier to treat. NCI also notes that screening tests can have possible harms, not just benefits: they may give false-positive results (suggesting cancer when there is none) or false-negative results, and can lead to overdiagnosis, finding cancers that would never have caused problems. NCI says a screening test should have more potential benefits than harms. This is general information, not personal medical advice.

Last updated: 2026-07-13

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