What Does a TP53 Mutation Mean?

NCI describes TP53 as a gene that makes a protein found inside the nucleus of cells. That protein plays a key role in controlling cell division and cell death. TP53 is a tumor suppressor gene.

MedlinePlus Genetics fills in how it works. The p53 protein attaches directly to DNA. If the DNA can be repaired, p53 switches on other genes to fix the damage. By stopping cells with damaged DNA from dividing, p53 helps prevent tumors from forming.

That job earned it a nickname, which MedlinePlus records: the guardian of the genome.

A mutation means that guard is not doing its job in the cells tested.

This is the number that reframes the whole result.

MedlinePlus Genetics states that acquired TP53 changes are the most common gene change found in human cancer, occurring in about half of all cancers.

It then gives the figures by type:

• lung cancer: nearly half. Small cell lung cancers nearly always carry one.
• ovarian cancer: almost half of tumors.
• head and neck squamous cell cancers: nearly half.
• breast cancer: 20 to 40 percent of all cases.

Reading TP53 on your report does not put you in a rare category. It puts you in the largest category there is.

This is the question that changes what happens next, and a tumor report usually cannot answer it.

Most TP53 changes are acquired. NCI defines an acquired, or somatic, change as one that happens after conception. It appears in the tumor and is not passed to children.

An inherited change is different. NCI describes a germline mutation as one carried in an egg or sperm, which then ends up in every cell of the child.

The two look similar on a tumor sequencing report. Telling them apart takes a separate germline test, usually on blood or saliva, with genetic counseling alongside it.

MedlinePlus Genetics makes an unusual statement about this gene. Although acquired TP53 changes appear in many cancers, Li-Fraumeni syndrome appears to be the only cancer syndrome linked to inherited mutations in TP53.

NCI describes the condition itself. It is rare and inherited. It raises the risk of many cancer types. Cancers often develop at an early age, and more than one type may occur in the same person.

MedlinePlus notes that at least 140 different TP53 mutations have been identified in people with the syndrome. Many of them change the part of the protein that binds to DNA.

If your family history includes several cancers, or cancers at young ages, that is worth raising when you discuss this result.

Honestly, usually less than people expect.

There is no standard therapy selected on TP53 status, the way HER2 or EGFR results select one. Its main role today is describing how a tumor behaves, and sometimes deciding whether a clinical trial is open to you.

One prognosis finding is worth reporting accurately, because it is real and it is limited. In breast cancer, MedlinePlus Genetics says tumors with TP53 mutations tend to have a poorer prognosis than those without. They are more likely to be aggressive, more likely to resist certain anti-cancer drugs and radiation, and more likely to come back after treatment.

That describes averages across studied groups. It is not a prediction about any one person, and it does not by itself decide your treatment.

Find out which sample it came from. Ask whether your team thinks it could be inherited. Ask whether a genetic counselor should be involved.

Then ask the more useful question. 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.

• MedlinePlus Genetics — TP53 gene
• NCI Dictionary of Cancer Terms — p53 gene
• NCI Dictionary of Cancer Terms — Li-Fraumeni syndrome
• NCI Dictionary of Cancer Terms — germline mutation
• NCI Dictionary of Cancer Terms — somatic mutation