What is TERT?

Reviewed by Pathologists on:
January 1, 2026

TERT is a gene that provides instructions for making part of an enzyme called telomerase. Telomerase helps maintain structures called telomeres, which protect the ends of chromosomes.

TERT is considered a biomarker. A biomarker is a measurable feature in a tumour, such as a gene change, that helps doctors understand how a cancer behaves and how aggressive it may be.

What is the function of TERT in normal cells?

Telomeres protect chromosomes and help keep DNA stable. Each time a normal cell divides, its telomeres become slightly shorter. When telomeres become too short, the cell can no longer divide and will eventually stop growing or die. This is a natural safety mechanism that helps prevent uncontrolled cell growth.

The TERT gene helps control telomerase activity. In most adult tissues, TERT is inactive or only weakly active, which allows telomeres to shorten over time. This limits how long cells can keep dividing and helps protect the body from cancer.

What types of cancer are associated with TERT?

Abnormal changes involving TERT are seen in many types of cancer. TERT alterations are widespread in:

  • Thyroid cancer, particularly aggressive types.

  • Brain tumours, such as gliomas.

  • Melanoma.

  • Bladder cancer.

  • Liver cancer.

TERT changes are uncommon in normal tissues, which is why they are helpful as cancer biomarkers.

How does TERT cause cancer?

Cancer cells often need a way to keep dividing without stopping. Changes in the TERT promoter, often called TERT promoter mutations, increase telomerase activity. This allows cancer cells to maintain their telomeres, thereby avoiding normal aging and cell death. As a result, tumour cells can divide repeatedly and survive much longer than they should.

TERT alterations do not usually cause cancer on their own, but they often work together with other genetic changes to make tumours more aggressive.

Why do pathologists test for TERT?

Pathologists test for TERT because it is an important prognostic biomarker, meaning it provides information about how a tumour is likely to behave.

In several cancers, the presence of a TERT promoter mutation is associated with more aggressive disease and a higher risk of recurrence. TERT testing can help doctors better estimate risk and guide decisions about follow-up and treatment intensity.

In some tumours, TERT results also help refine the diagnosis when used alongside other biomarkers.

How do pathologists test for TERT?

TERT testing is usually performed on tumour tissue obtained from a biopsy or surgery. In some situations, it may also be tested using a blood sample, called a liquid biopsy, to detect tumour DNA in the bloodstream.

Common testing methods include:

  • Polymerase chain reaction (PCR)–based tests to detect TERT promoter mutations

  • Next-generation sequencing (NGS), which can analyze TERT along with many other cancer-related genes

The choice of test depends on the tumour type and the clinical question.

How do TERT results appear in a pathology report?

TERT results are usually found in sections of the pathology report labeled molecular testing, biomarker studies, or ancillary studies.

Results are commonly reported as:

  • TERT promoter mutation detected, often with the specific mutation listed

  • No TERT promoter mutation detected

The report may also include a comment explaining whether the TERT result is associated with a higher-risk or more aggressive tumour type.

How does TERT fit with other cancer biomarkers?

TERT is rarely interpreted on its own. It is often evaluated together with other biomarkers that affect tumour growth and behaviour.

For example, in thyroid cancer, TERT results are commonly interpreted alongside markers such as BRAF or RAS. Tumours with both TERT and other driver mutations often behave more aggressively than tumours with only one change.

In brain tumours, TERT is assessed with biomarkers such as IDH status and chromosomal changes to help classify the tumour and estimate prognosis.

Combining TERT with other biomarkers allows pathologists to provide more accurate diagnostic and prognostic information.

Questions to ask your doctor

  • Was my tumour tested for TERT?

  • Was a TERT promoter mutation found?

  • How do my TERT results affect prognosis?

  • Were other biomarkers tested at the same time?

  • Do my TERT results change how my cancer will be monitored or treated?

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