Menu
Get Help Now Larger text

The words on your gene results, one by one

What each gene test on a brain tumor report measures. What your team uses each one for, and what it does not tell you. Includes whether these results are passed on to children.

The short version

Your report may carry short words like IDH, MGMT or 1p/19q. They are results of tests done on the tumor tissue. This page says what each one measures and what your team uses it for. It does not say what your own result means. That answer belongs to your team, who can see your whole report and know the rest of your story.

What these tests are

The lab tests the tumor tissue itself.

Genes are small pieces of DNA. They are the instructions inside cells. The lab looks for changes in those instructions in the tumor cells, and for other marks it can stain for.

Under the rules brought in for 2021, many of these results are part of the name of the tumor. They are not extra notes at the end. That is why the name on a report can gain words while you wait.

So these are labels on the tumor. They say what the lab found. Reading them is not the same as knowing what will happen to you.

Are these results passed on to my children?

No. The lab looked at the tumor, not at you.

Changes found this way are called somatic. They happened in the tumor cells during your life. The National Cancer Institute puts it plainly: somatic changes cause most cancers and cannot be passed on to family members.

This kind of testing has its own name. Across cancer groups it is called biomarker testing, and the agreed meaning is testing for markers that are not inherited. Looking for something that runs in a family is a different test.

Once in a while a tumor test does turn up a change a person was born with. If that happens your team would tell you, and they would offer you a second test and someone to talk it through with. It is not something that gets decided without you.

Where these words sit on your report

They usually sit in their own part of the report, under a heading about gene or molecular results. Sometimes they arrive as a separate report of their own, days or weeks after the first one.

Your pathology report, part by part walks through the whole document and where each part sits.

The words, one by one

Each one below says what is measured, what your team does with it, and what it does not tell you. They are read together, never one at a time.

IDH

What is measured. Whether the tumor cells carry a change in one of two genes, IDH1 or IDH2. A stain finds the most common single change. If the stain shows nothing, the lab reads the gene itself, because rarer changes do not show up on the stain.

What your team does with it. It has to be tested on every diffuse glioma: A glioma whose cells spread out into the brain around it instead of staying in one lump. That is why the edge on a scan is not a clean line. See the glossary, and it is usually the first answer they wait for. The result becomes part of the name of the tumor.

What it does not tell you. The words mutant and wildtype are names, not scores. They tell you which set of naming rules your tumor falls under, and nothing on their own about you.

1p/19q co-deletion

What is measured. Chromosomes are the packages DNA is stored in. This test asks whether the tumor cells have lost one whole arm of chromosome 1 and one whole arm of chromosome 19, both together.

What your team does with it. In a glioma: A tumor that starts in the glial cells. Those are the support cells of the brain and spinal cord. Gliomas are given a grade from 1 to 4. The grade says how the tumor is expected to act. See the glossary that also has an IDH change, this is the finding that makes the tumor an oligodendroglioma. The name follows the test.

What it does not tell you. Whole arms are the point. A test that finds only part of an arm missing is a different result, and your report may say so. Some methods can only see part of an arm, which is why the lab may repeat it a different way.

ATRX

What is measured. Whether the tumor cells still make the ATRX protein. A stain shows it as kept or lost. The gene can also be read directly.

What your team does with it. It helps tell one kind of glioma from another. In oligodendroglioma the protein is usually kept. In astrocytoma it is often lost.

What it does not tell you. By itself it names nothing. It is one of the findings your team lines up beside the IDH result.

TERT promoter

What is measured. A promoter is the switch that turns a gene on. This test asks whether the switch for the TERT gene carries a change. In a meningioma, finding one sets the grade at 3 on its own.

What your team does with it. When the IDH test shows no change, this is one of three findings that can point to a glioblastoma: A glioma that is given grade 4. Grade 4 is the highest grade there is. The tumor grows fast. Treatment usually starts soon after it is found. It often means surgery, and then radiation and chemotherapy. See the glossary even when the cells look like a lower grade under the microscope. In a tumor that does have an IDH change, it is read differently.

What it does not tell you. It turns up in more than one kind of tumor, so on its own it does not name one.

CDKN2A/B

What is measured. Whether both copies of two neighboring genes are gone. Everyone has two copies of most genes. Losing both is written CDKN2A/B homozygous deletion.

What your team does with it. In some gliomas this finding sets the grade on its own, even when the cells look like a lower grade.

What it does not tell you. A grade is a description of the tumor, not a countdown. What the grade means explains how grades are worked out and why the numbering changed in 2021.

EGFR

What is measured. Whether the tumor cells carry extra copies of the EGFR gene. Extra copies are called amplification, so a report may say EGFR amplification.

What your team does with it. When the IDH test shows no change, this is the second of three findings that can point to a glioblastoma even when the cells look like a lower grade.

What it does not tell you. Extra copies in tumor cells are not a change in the genes you were born with. They happened in the tumor.

Chromosome 7 and chromosome 10

What is measured. Whether the tumor cells have gained a whole copy of chromosome 7 and lost a whole copy of chromosome 10. It is often written +7/-10.

What your team does with it. When the IDH test shows no change, this is the third of three findings that can point to a glioblastoma even when the cells look like a lower grade.

What it does not tell you. This is a count of whole chromosomes rather than a test of one gene, so it will not show up in a list of genes.

H3 K27-altered

What is measured. Histones are the spools that DNA winds around. The lab looks for the loss of a chemical mark on one of them, or for a change in the gene that makes it. The change is written K27M.

What your team does with it. In a diffuse glioma sitting in the middle of the brain or the spine, this finding names it a diffuse midline glioma.

What it does not tell you. You may see this written two ways. Older reports say H3 K27M, after the one change. The 2021 rules say H3 K27-altered, because more than one route leads to the same place. Both may be describing the same tumor.

H3 G34

What is measured. A change at a different spot on the same kind of histone gene. The spot is written G34, so the finding is written H3 G34.

What your team does with it. It names a diffuse hemispheric glioma. It is usually seen along with a loss of ATRX and a p53 stain that lights up.

What it does not tell you. It is a separate finding from H3 K27, not a version of it. The two point to different tumors that sit in different places.

BRAF

What is measured. Two different things can be looked for. One is a single change written V600E. The other is BRAF joined onto a neighboring gene, which is called a fusion.

What your team does with it. It helps name some tumors. There are also drugs made to act on BRAF changes, so your team may test for it with treatment in mind.

What it does not tell you. Finding a change does not mean a drug is right for you. Whether one is an option depends on the whole picture, and it is a conversation to have with your team. Targeted drugs covers what that conversation is about, for BRAF and for the other changes a drug exists for.

MGMT promoter methylation

What is measured. MGMT is a gene. Its protein repairs one kind of damage that some chemotherapy drugs do to DNA. Methylation is a chemical tag that can quiet the switch that turns a gene on. The lab measures how many places on that switch carry the tag, so the answer is a quantity rather than a plain yes or no.

What your team does with it. Most of the results on this page are used to name the tumor. This one is different. They use it as one input when they are choosing chemotherapy for a glioblastoma.

What it does not tell you. The line between methylated and unmethylated is not settled. Labs use different tests and different cut-off points, and when two of those tests disagree about the same sample it is not known which one to go with. The result is also only used this way for one kind of tumor. So it is something your team weighs up rather than an answer on its own, and what yours means is a question for them.

Ki-67

What is measured. A stain that marks cells that were dividing at the moment the sample was taken. It is reported as the share of tumor cells that took up the stain, written as a percentage. You may see it called MIB-1.

What your team does with it. They read it next to everything else on the report.

What it does not tell you. There is no agreed way to count it. Nobody has settled which cells to count or which part of the slide to pick, so the same slide can be scored differently by different people. A small difference between one report and another is not something to read anything into.

TP53

What is measured. Whether the TP53 gene in the tumor carries a change. A stain for the protein it makes is sometimes used instead.

What your team does with it. It is one of the findings that fits with an astrocytoma that also has an IDH change.

What it does not tell you. Finding it in the tumor is not the same as inheriting it. Changes you were born with are looked for by a different test, and your team would talk to you first.

Gene panels

What is measured. One test that reads many genes at once from the tumor sample. It is called a gene panel. Panels that read DNA find small changes and missing or extra copies. Panels that read RNA are better at finding two genes joined together.

What your team does with it. One test instead of several, with the results arriving as a list.

What it does not tell you. The report lists every gene the test looked at, not only the ones that had changed. A long list is a list of what was checked.

Methylation profiling

What is measured. The same kind of chemical tag as the one in the MGMT test, but read right across the tumor's DNA, at about 850,000 places at once. Reading it that way is called methylation profiling. The pattern is then compared with a library of thousands of brain tumors that have already been named.

What your team does with it. It helps place a tumor with a type. The report comes back with a score for how closely the pattern matched. The same test also shows whole chromosomes that have been gained or lost.

What it does not tell you. A low score means the pattern did not match any group closely enough to call it. It is a statement about the match, not a finding about the tumor.

How long do these take?

Longer than the part that comes from the microscope. For most of them it is weeks rather than days. That is why a report can turn up in pieces, and why the first version of yours may say that some results are still to come.

Waiting for your pathology results covers the whole wait: what is being done to your tissue, why some of it takes weeks, and what you can do in the meantime.

Who explains my result?

Your own team. This page says what each test measures. It cannot say what your result means, because that depends on the rest of your report and on you.

The doctor who ordered the tests is the one who goes through them with you. If a word on your report does not match a word here, ask about it. Reports are written for doctors, and the same finding can be written more than one way from one lab to the next.

What to ask your team

Where to go next

This is not medical advice. It explains research in plain words. Your care team knows your case. Talk with them before you make any decision about your treatment.

Last reviewed: September 3, 2026

Sources for this page: