The short answer
TP53 makes a protein that stops damaged cells from dividing. Acquired changes in it are the most common gene change in human cancer, found in about half of all cancers. Whether the change is in the tumor only, or in every cell you have, is the question that decides what happens next.
The p53 protein binds directly to DNA and stops cells with damaged DNA from dividing, which is why it is nicknamed the guardian of the genome.
Acquired TP53 changes are the most common gene change found in human cancer, present in about half of all cancers.
Li-Fraumeni syndrome appears to be the only cancer syndrome linked to inherited TP53 mutations.
A tumor report cannot tell you on its own whether a change is inherited; that needs a separate germline test.
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This page is for people who see a TP53 mutation on a tumor genetic test report. It explains what the gene does, how common the change is, when it might be inherited, and what it means for prognosis.
The gene that stops damaged cells dividing
TP53 makes a tumor suppressor protein, p53, that regulates cell division. MedlinePlus Genetics says that when DNA is damaged, p53 activates other genes to fix it. If the damage cannot be repaired, p53 prevents the cell from dividing and signals it to self-destruct. That job earned it the nickname "the guardian of the genome."
A mutation means that guard may not be doing its job in the cells tested.
It is the commonest gene change in human cancer
MedlinePlus Genetics states that acquired (somatic) TP53 changes are the most common gene changes found in human cancer, occurring in about half of all cancers. It gives figures by type:
- lung cancer: nearly half. Small cell lung cancers nearly always have one.
- ovarian cancer: almost half of tumors.
- head and neck squamous cell cancers: nearly half.
- breast cancer: 20 to 40 percent of all cases.
Seeing TP53 on your report does not put you in a rare category.
Acquired in the tumor, or inherited?
Most TP53 changes in tumors are acquired, meaning they arose in the cancer and were not born with you. NCI says some biomarker tests can find changes you were born with, and that biomarker testing is different from genetic testing for inherited mutations. A tumor report may not tell you which kind you have. Genetic counseling may be recommended.
Li-Fraumeni syndrome
MedlinePlus Genetics says Li-Fraumeni syndrome appears to be the only cancer syndrome linked to inherited TP53 mutations. It raises the risk of cancers such as breast cancer, bone cancer, and soft tissue sarcomas. At least 140 different TP53 mutations have been found in people with the syndrome. Many change the part of the protein that binds to DNA.
If your family history includes several cancers, or cancers at young ages, raise that when you discuss this result.
What it may mean for prognosis
In breast cancer, MedlinePlus Genetics says tumors with TP53 mutations tend to have a poorer outlook than those without. They are more likely to be aggressive, to resist certain anti-cancer drugs and radiation, and to come back after treatment.
That describes averages across studied groups. It is not a prediction about any one person.
What to do with this line on your report
Questions to ask your care team:
- Which sample did this result come from?
- Could this change be inherited?
- Should a genetic counselor be involved?
- On this report, which finding is actually driving the plan?
Genetic Testing vs Genomic Testing explains the tumor and inherited split. Genetic Testing After a Cancer Diagnosis is a good list to bring if germline testing comes up.
Sources
Common questions
Is a TP53 mutation rare or serious?
It is not rare. MedlinePlus Genetics says acquired TP53 changes are the most common gene change found in human cancer, occurring in about half of all cancers. Seeing it on a report puts you in a very large group, not a small unusual one.
Does this mean my family is at risk?
Only if the change is inherited, and a tumor test cannot tell you that. Inherited TP53 changes cause Li-Fraumeni syndrome, which MedlinePlus describes as apparently the only cancer syndrome linked to inherited mutations in this gene. Confirming it takes a separate germline test.
Is there a drug that targets TP53?
There is no standard treatment chosen on TP53 status in the way HER2 or EGFR results choose one. Its main use today is describing tumor biology, and sometimes deciding eligibility for a clinical trial.
What does p53 mean if my report says that instead?
They are the same thing. NCI lists p53 gene, TP53 gene and tumor protein p53 gene as names for one gene. Reports may also describe abnormal p53 staining, which is a stain looking for the protein rather than a reading of the gene.
Questions to ask your doctor
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Sources last checked: 2026-08-09 what this meansLast updated: 2026-08-11Next planned review: 2027-08-09
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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