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Glossary

Plain words for the medical terms you will hear. Any word with a dotted line under it opens its meaning here.

1

1p/19q co-deletion

Two pieces of two chromosomes are gone. They are gone from the tumor cells. A glioma can have this change. If it has an IDH gene change too, it is called an oligodendroglioma.

Also called: 1p/19q codeletion, 1p/19q.

Where this came from:

5

5-ALA

A medicine you are given before some brain operations. The tumor soaks it up. Under a special light the tumor then glows, so the surgeon can see where it stops and healthy brain starts.

Also called: fluorescence-guided surgery.

Where this came from:

A

addendum (uh-DEN-dum)

A part added to a report that has already been sent out. It holds results that were not ready the first time. An addendum is not a correction, and it does not mean anything went wrong.

Also called: addendum report.

Where this came from:

adult-type

A group of gliomas sorted by their biology. Not by the age of the person who has them. Adults usually have one of these. And children sometimes do too. Seeing it on your report is not a filing mistake.

Also called: adult-type glioma, adult-type diffuse glioma.

Where this came from:

advance directive

A written note of what you want done, and who speaks for you, if you cannot speak for yourself. A living will is one kind. If you have one, bring it in before an operation.

Where this came from:

amended report

A report where something already written has been changed. It was not added to. It is labeled as amended. It normally says what changed and why. Most changes are small ones, like a typing mistake.

Also called: amendment.

Where this came from:

anesthesiologist

The doctor who puts you to sleep for an operation. They look after you while you are under. They see you before the day too. They check that an anesthetic is safe for you.

Where this came from:

astrocyte (AS-troh-site)

A star-shaped helper cell in the brain and spinal cord. It is one of the glial cells that sit around nerve cells. An astrocytoma starts in these.

Also called: astrocytes.

Where this came from:

ATRX

A gene checked on the pathology report. The tumor cells may or may not still make the ATRX protein. Which one it is helps sort a glioma into one type or another.

Where this came from:

awake craniotomy

Surgery where you are awake for part of it and asked to talk or move, so the team can check those parts of the brain are not harmed. The brain feels no pain, and your scalp is numbed.

Where this came from:

B

bevacizumab (BEV-uh-SIZ-oo-mab)

A drug that acts on the blood vessels a tumor builds. In brain tumors it is used mainly for two things. One is to control symptoms from swelling. The other is to cut down how much steroid someone needs.

Where this came from:

blood thinner

A medicine that makes it harder for your blood to clot. Aspirin is one. And there are several others. Never stop one on your own before an operation. Your team decides that. And each medicine is different.

Also called: blood thinners.

Where this came from:

bone flap

The piece of skull bone taken out so a surgeon can reach the brain. It is put back at the end of the operation and held in place.

Where this came from:

BRAF

A gene in a pathway that tells cells to divide. Some tumors carry a change in it. There are drugs made to target that change, so your team may test for it.

Also called: BRAF V600E, BRAF fusion.

Where this came from:

brain mapping

Finding out which parts of your brain do which jobs, like speech or movement. A scan before an operation can do it. It can also be done during one. Then small spots are tested with a tiny electric current.

Where this came from:

C

calcification (KAL-sih-fih-KAY-shun)

Calcium built up inside a tumor. It shows as bright specks on a CT scan. It is common in oligodendroglioma, and the pattern can point to that diagnosis. It is not something you did.

Also called: calcifications, calcified.

Where this came from:

carmustine wafer (kar-MUS-teen)

A small wafer that holds chemotherapy and melts away. A surgeon puts it in the space where a tumor was. This is done during the surgery. That way the drug acts close to that spot.

Also called: carmustine wafers, Gliadel.

Where this came from:

CDKN2A/B homozygous deletion

Both copies of two genes that put the brakes on cell division are missing. The two are CDKN2A and CDKN2B.

Also called: CDKN2A/B deletion, CDKN2A/B.

Where this came from:

chemoradiation (KEE-moh-ray-dee-AY-shun)

Radiation and chemotherapy over the same weeks. They are given together. Not one after the other. It is the usual plan for glioblastoma, IDH-wildtype. Some other tumors get the two apart. What you get depends on your tumor type.

Also called: chemoradiotherapy, Stupp protocol.

Where this came from:

chromosome 7 gain and chromosome 10 loss

The tumor cells gained a whole copy of chromosome 7. They also lost a whole copy of chromosome 10. The IDH test may show no change. This is then one of the findings that can name a glioblastoma.

Also called: +7/-10.

Where this came from:

circumscribed

A tumor with an edge. It sits apart from the brain around it rather than growing into it. It is the opposite of diffuse. That is why some of these can be cured by an operation.

Where this came from:

CNS WHO grade

A number from 1 to 4 for how a tumor is likely to behave. Since 2021 it is written in plain numbers, not Roman ones. Gene results can set it too.

Also called: WHO grade.

Where this came from:

contrast dye

A liquid put into a vein before some scans. It makes certain tissues stand out, which helps show where a tumor is. It does not always show the whole of it.

Also called: gadolinium, contrast agent.

Where this came from:

craniectomy (kray-nee-EK-tuh-mee)

The same operation as a craniotomy, but the piece of skull is not put back yet. That leaves room in case the brain swells.

Where this came from:

craniotomy (kray-nee-OT-uh-mee)

An operation that opens a window in the skull to reach the brain. The piece of bone is put back at the end and fixed in place.

Where this came from:

D

debulking

Surgery to take out as much tumor as is safe, when taking all of it is not the plan. Less bulk can mean less pressing on the brain.

Where this came from:

dexamethasone (dek-suh-METH-uh-sone)

A steroid medicine given to bring down swelling around a tumor. It is not chemotherapy. It has its own side effects, so your team lowers the dose when they can.

Also called: Decadron.

Where this came from:

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.

Where this came from:

dural tail

A streak of thickened covering next to the tumor on a scan. It is a common sign on a meningioma scan. Other things can cause it too.

Where this came from:

E

EGFR amplification

The tumor cells carry extra copies of the EGFR gene. It is one of the findings your team reads next to the IDH result. They read both when naming an adult glioma.

Where this came from:

eloquent cortex

Parts of the brain that do a job you would notice losing, like speech, movement or sight. Surgery near them is planned with extra care.

Also called: eloquent area, eloquent region.

Where this came from:

embryonal tumor

A tumor that grows from very early forms of nerve cells, the kind found in a developing nervous system. Several childhood brain tumors are grouped this way. An older name for some of them was PNET.

Also called: embryonal tumors.

Where this came from:

extra-axial

Growing outside the brain itself, not inside it. A meningioma is one. It starts in the layers around the brain and presses inward.

Also called: extraaxial.

Where this came from:

F

FLAIR

One of the picture settings used in an MRI. It dims the fluid in the brain so that swelling and other changes show up more clearly.

Where this came from:

focal seizure

A seizure that starts in one part of the brain. Some people stay aware through it: twitching, an odd smell, a feeling hard to name. Others lose awareness, and that kind used to be called complex partial.

Also called: complex partial seizure.

Where this came from:

fractionation

Splitting radiation into many small treatments instead of one big one. Each one is called a fraction. It gives healthy tissue time to repair in between.

Also called: fractionated radiation.

Where this came from:

frontal lobe (FRUN-tul lobe)

The part of the brain above and behind your forehead. There are two, one on each side, and they are the largest of the brain's four lobes.

Also called: frontal lobes.

Where this came from:

frozen section

A quick look at a piece of tissue while you are still in the operating room. It can guide the operation, but it is not the final diagnosis.

Where this came from:

functional MRI

An MRI that watches blood flow while you do simple tasks. It shows which part of your brain does a job like speech or movement. It helps plan surgery, and a team may check the same question again during it.

Also called: fMRI.

Where this came from:

G

gene panel

One lab test that checks many genes at the same time. It is run on your tumor tissue, not on you. It is one of the tests that takes weeks rather than days.

Also called: gene panel test.

Where this came from:

glioblastoma (glee-oh-blas-TOH-muh)

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.

Also called: GBM.

Where this came from:

glioma (glee-OH-muh)

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.

Where this came from:

gross description

The part of a pathology report that describes the tissue as it looks to the naked eye. It notes the size, the color, and how the tissue felt. Here "gross" means seen without a microscope. It does not mean unpleasant.

Where this came from:

gross total resection

No tumor is left that can be seen on the scan taken after surgery. It is judged by that scan, not by what the surgeon saw in the room.

Also called: complete resection.

Where this came from:

H

H3 G34

A change in a histone. A histone is a protein DNA wraps around. A diffuse glioma can have it. Then it is called a diffuse hemispheric glioma. H3 K27 is a different finding, but on the same kind of gene.

Also called: H3 G34-mutant.

Where this came from:

H3 K27-altered

A change in a histone. A histone is a protein DNA wraps around. A diffuse glioma can have it. If it also sits in the middle of the brain or spine, it is called a diffuse midline glioma.

Also called: H3 K27M, K27M.

Where this came from:

hydrocephalus (hy-droh-SEF-uh-lus)

Fluid building up inside the brain because it cannot drain the usual way. It raises the pressure in the skull. There are treatments to let it drain again.

Where this came from:

I

IDH gene change

A small change in a tumor's IDH gene. It is the first thing your team looks at when naming an adult glioma, and it can affect which treatments are offered. Your pathology report says whether your tumor has it.

Also called: IDH mutation, IDH-mutant, IDH, IDH1, IDH2.

Where this came from:

immunohistochemistry (IM-yoo-noh-HIS-toh-KEM-is-tree)

A way of staining a slide to show whether one protein is there in the cells. Each stain answers one question, so a report may list several of them.

Also called: special stains.

Where this came from:

integrated diagnosis

The final diagnosis. It is made by putting what the cells look like together with the gene test results. For many brain tumors both parts are needed to name it.

Where this came from:

K

Ki-67

A stain that shows how many tumor cells were dividing when the sample was taken. The report gives it as a percentage. It is read together with everything else, not on its own.

Also called: Ki-67 index, MIB-1.

Where this came from:

L

laser ablation

Using heat from a laser to destroy tumor tissue. The laser goes in through a small hole in the skull, not a large opening. It suits some tumors and not others. Not every hospital offers it.

Also called: LITT, laser interstitial thermal therapy.

Where this came from:

levetiracetam (lee-veh-tie-RA-suh-tam)

A medicine that helps stop seizures. Many people with a brain tumor take it. In some people it also brings a short temper, anger or low mood. Tell your team if you notice that.

Also called: Keppra.

Where this came from:

linear accelerator

The machine that gives external radiation. It moves around you and aims the beam. Like an x-ray, the radiation from it is painless.

Also called: linac.

Where this came from:

lomustine (loh-MUS-teen)

A chemotherapy you take as a capsule. You take it now and then, not every day. It lowers your blood counts weeks after a dose. That is why the doses are spaced out.

Also called: CCNU.

Where this came from:

M

mass effect

The tumor is taking up room and pushing on what is next to it. The skull cannot stretch, so anything that takes up space presses on the brain around it.

Where this came from:

memantine (meh-MAN-teen)

A medicine given with whole-brain radiation to help protect thinking and memory.

Also called: Namenda.

Where this came from:

methylation profiling

A lab test that reads a chemical pattern across the tumor's DNA. The pattern is a bit like a fingerprint. It is matched against a library to help name the tumor type.

Also called: DNA methylation profiling, methylation array.

Where this came from:

MGMT promoter methylation

MGMT is a gene whose protein repairs damage to a tumor's DNA. Methylation turns it down. Your report says how much, and your team uses that when they choose chemotherapy. The line between high and low is not settled.

Also called: MGMT, MGMT methylation, methylated MGMT.

Where this came from:

microvascular proliferation

Clumps of tiny new blood vessels the pathologist sees in the sample. It is one of the things looked for when setting the grade.

Where this came from:

N

nadir (NAY-deer)

The lowest point your blood counts reach after a dose of chemotherapy. It is usually about a week to ten days later. And it is when infection is most of a risk.

Where this came from:

NEC

Short for "not elsewhere classified". The tests were done, but the results do not match any named tumor type. Ask your team what it means for your plan.

Also called: not elsewhere classified.

Where this came from:

neuro-oncologist (NOOR-oh-on-KOL-uh-jist)

A doctor who specializes in tumors of the brain and spine. They often lead the brain tumor team. They are a good person to ask who your one named contact is.

Where this came from:

neuronavigation (NEW-roh-nav-ih-GAY-shun)

A map of your head that a surgeon follows during surgery. It is built from a scan taken beforehand. Stickers on your scalp, or the shape of your face, line it up with you.

Also called: navigation scan, image guidance.

Where this came from:

neuropathologist (NEW-roh-path-OL-oh-jist)

A doctor who works out what a tumor is by looking at the tissue itself. They specialize in the brain and the nerves. You do not usually meet them, but they are the person who names your diagnosis.

Also called: neuropathology.

Where this came from:

neuropsychologist (NEW-roh-sy-KOL-oh-jist)

A psychologist who looks at how a brain problem changes thinking. They read the tests of memory, attention and language. Then they write the report that says what would help.

Also called: neuropsychological testing, neuropsychological, neuropsychology.

Where this came from:

neutropenia (noo-troh-PEE-nee-uh)

Having too few of the white blood cells that fight infection. It is a common effect of chemotherapy. And it is why you have to report a temperature at once.

Also called: low white blood cell count.

Where this came from:

NOS

Short for "not otherwise specified". It means the gene tests needed to name the tumor fully were not done or could not be done. Ask your team whether they can be.

Also called: not otherwise specified.

Where this came from:

O

oligodendrocyte (OL-ih-goh-DEN-droh-site)

A helper cell in the brain and spinal cord. It wraps nerve fibers in a fatty coat called myelin, which helps nerve signals move. An oligodendroglioma starts in cells that look like these.

Also called: oligodendrocytes.

Where this came from:

P

palliative care

Care that helps with pain and other symptoms. It supports the whole family too. It can start early. It includes help with making choices about treatment.

Where this came from:

PCV (pee-see-VEE)

Three chemotherapy drugs given together: procarbazine, lomustine and vincristine. It is the usual choice after radiation for an oligodendroglioma.

Where this came from:

pediatric-type

A group of gliomas sorted by their biology. Not by the age of the person who has them. Adults are sometimes diagnosed with one. The name is about how the tumor acts, not who it belongs to.

Also called: pediatric-type glioma, pediatric-type diffuse glioma.

Where this came from:

pons

A part of the brain stem. The nerve paths for eye movement, hearing, speaking, swallowing and balance pass through it. So do the paths for movement in your arms and legs.

Where this came from:

posterior fossa (pos-TEER-ee-er FOSS-uh)

The space low at the back of the skull. It holds the cerebellum, which helps with balance, and the brain stem.

Where this came from:

posterior fossa syndrome

Something that can happen after an operation on the lower back of the brain. Some children cannot speak for a while. Swallowing, walking and mood can change too. It always starts in the first week after surgery.

Also called: cerebellar mutism syndrome, cerebellar mutism.

Where this came from:

procarbazine (pro-KAR-buh-zeen)

A chemotherapy taken as a capsule. It is the P in the PCV combination used for some gliomas.

Where this came from:

pseudoprogression (SOO-doh-pro-GRESH-un)

A scan after treatment that looks worse because of the treatment itself. It is not because the tumor has grown. Telling the two apart can take another scan.

Where this came from:

R

radiation mask

A mesh shell shaped to your face and head. It holds your head in the same place for every treatment. You can see through it and breathe through it, and it does not hurt.

Also called: thermoplastic mask.

Where this came from:

radiation necrosis (neh-KROH-sis)

Damaged tissue where radiation was aimed, months or years later. On a scan it can look like tumor coming back. Telling the two apart can take more scans, and sometimes a sample.

Where this came from:

radiation oncologist

The doctor in charge of radiation treatment. They decide which area is treated, and how the treatment is split up.

Where this came from:

radiologist

A doctor trained to read scans and write down what they show. The report goes to the doctor who asked for the scan, who then tells you. One who specializes in the brain and spine is called a neuroradiologist.

Also called: neuroradiologist.

Where this came from:

RANO

Short for Response Assessment in Neuro-Oncology. An agreed set of rules for judging whether a tumor has changed. It uses the scan, your steroid dose, and how you are doing.

Also called: Response Assessment in Neuro-Oncology.

Where this came from:

rescue medicine

A medicine kept at home to stop a seizure that is going on too long. Depending on which one your doctor picks, it goes up the nose, under the tongue, or into the bottom.

Also called: rescue medication.

Where this came from:

S

seizure action plan

A short written page that says what your seizures look like, what people should do, whether you have a rescue medicine, and who to call. You keep copies where they will be needed.

Where this came from:

simulation

The planning visit before radiation starts. No radiation is given. Your mask is made. And a scan is taken in the exact position you will be treated in.

Also called: CT simulation, planning session.

Where this came from:

SMA syndrome

Trouble starting to speak, and to move one side of the body. It comes on right after surgery near the part of the brain that starts movement. It usually eases within days, and goes on easing for weeks after that.

Also called: supplementary motor area syndrome.

Where this came from:

somnolence syndrome (SOM-noh-lens)

Heavy drowsiness, poor focus and tiredness. It comes in the weeks after radiation to the head ends. It usually clears up on its own, with no treatment. That takes a few weeks.

Where this came from:

status epilepticus (STAY-tus ep-ih-LEP-tih-kus)

A seizure that lasts more than five minutes. Or seizures one after another, with no waking up in between. This one is an emergency. Call an ambulance.

Where this came from:

stereotactic biopsy

Taking a small sample through a narrow opening in the skull, guided by a scan. A full opening is not made. It is used when the area to be sampled is hard or risky to reach.

Also called: needle biopsy.

Where this came from:

stereotactic radiosurgery

Radiation aimed at a small target, in one visit or a few. There is no cutting, despite the name.

Also called: SRS, Gamma Knife, CyberKnife.

Where this came from:

subtotal resection

Some tumor is still seen on the scan taken after surgery. Surgeons stop short when going further would risk something you would not want to lose.

Where this came from:

supratentorial (soo-pruh-ten-TOR-ee-ul)

In the upper part of the brain, above the sheet of tissue that separates it from the lower part. Most adult gliomas are found here.

Where this came from:

T

temozolomide (tem-oh-ZOH-loh-mide)

A chemotherapy taken as a capsule, used for some brain tumors. Your team checks your blood counts while you are on it.

Also called: Temodar, TMZ.

Where this came from:

TERT promoter mutation

A change in the switch that controls the TERT gene. It keeps tumor cells from aging out. It is one of several findings your team reads together to name the tumor.

Also called: TERT.

Where this came from:

thalamus

A part deep in the brain, near its center. It passes messages from the senses and the body on to the rest of the brain.

Where this came from:

tonic-clonic seizure (TON-ik KLON-ik)

The kind of seizure most people picture. The muscles stiffen, then the arms and legs jerk, and the person is not awake for it. Most last one to three minutes. An older name is grand mal.

Also called: grand mal.

Where this came from:

TP53

A gene checked on the tumor tissue. Whether it has changed is one of the findings used to name an astrocytoma. Ask your team whether the change they found was in the tumor only.

Also called: p53.

Where this came from:

transformation

When a glioma changes into a higher grade over time. It is a known behavior of these tumors. And it is one of the things follow-up scans look for.

Also called: malignant transformation.

Where this came from:

tumor board

A meeting where specialists talk through one person's case together: the surgeon, the cancer doctor, the lab, and whoever read the scans. You are not there. What they decide is advice your own doctor goes through with you.

Also called: multidisciplinary tumor board, brain tumor board.

Where this came from:

tumor treating fields

A treatment that makes it harder for tumor cells to divide. It uses electric fields that switch back and forth. The fields come from pads on the scalp. A box you carry drives them. The box is often called Optune.

Also called: Optune.

Where this came from:

V

vasogenic edema

Fluid that leaks out of blood vessels. It leaks into the brain around a tumor. It is the swelling that steroid medicines are given to bring down.

Also called: vasogenic oedema, peritumoral edema.

Where this came from:

vincristine (vin-KRIS-teen)

A chemotherapy given into a vein. It is the V in PCV. It can cause numbness or tingling in the hands and feet, which is worth reporting early.

Where this came from:

vorasidenib (vor-uh-SID-eh-nib)

A medicine approved in 2024 for some people with a grade 2 glioma. The glioma has to have an IDH change. The medicine acts on that change itself. It is taken after surgery.

Also called: Voranigo.

Where this came from:

W

watch and wait

Following a tumor with scans at set times instead of treating it right away. It is a plan, not a delay. It is chosen to put off the costs of treatment. Treatment starts if it is needed.

Also called: active surveillance, watchful waiting.

Where this came from:

whole-brain radiation

Radiation given to the whole brain, rather than aimed at one spot. It is used when there are too many tumors to aim at one at a time.

Also called: whole brain radiation, WBRT.

Where this came from: