What is brain tumors?

A brain tumor is a growth of abnormal cells in or near the brain. Some brain tumors are cancer and some are not. Even a tumor that is not cancer can cause problems, because the skull has little room to spare. A primary brain tumor starts in the brain. The most common ones in adults are meningiomas and gliomas. A glioma starts in the support cells of the brain, called glial cells. Glioblastoma is the most common fast-growing primary brain cancer in adults.

When should I call my care team?

A seizure, especially a first one, one that lasts more than 5 minutes, or seizures back to back; Sudden severe headache, or a headache with vomiting; New weakness, numbness, or drooping on one side of the face or body; New trouble speaking, understanding, or seeing; New confusion, extreme sleepiness, or hard to wake up; Fever of 100.4 F (38 C) or higher, or chills, during chemotherapy; Unusual bleeding or bruising; Swelling or pain in one leg, or sudden shortness of breath or chest pain; Redness, swelling, or fluid leaking from your surgery cut; Running out of, or being unable to take, your seizure medicine or steroids; If it feels very bad, call 911.

Brain tumors

Brain tumors differ a lot from one another. Knowing your exact type helps your care team plan the best care for you.

Hi, I'm Rosa. Today we'll go through brain tumors together, one step at a time. I'll keep it simple, and you can pause me, go back, or skip ahead whenever you like. Just so you know, this is for learning only. It is not medical advice, so please check everything with your own doctor and care team. Okay, let's get started.

What a brain tumor is

Let's start with what a brain tumor is. It is a growth of abnormal cells in or near the brain. Some brain tumors are cancer, and some are not. Even a tumor that is not cancer can cause problems. That is because the skull has little extra room. Some tumors start in the brain. Others start somewhere else and spread to the brain. Brain tumors can cause headaches, seizures, or weakness. They can also change speech, vision, or mood. Your care team will explain your type.

The main types

Let's talk briefly about the types. Glioblastoma is a fast-growing tumor of the brain's support cells. Some slower-growing tumors have a gene change that helps doctors name them. Meningioma grows from the thin covering of the brain. Most meningiomas are not cancer. Brain metastases are cancers that spread from another body part. Lung, breast, and skin cancer are common sources. Lymphoma can start in the brain too. Some rarer tumors are seen more in children. Your care team will tell you which type you have.

Tests you may have

Now let's talk about tests. An MRI with dye is the main test. It shows the size and place of the tumor. A CT scan is fast and often done first in the emergency room. A brain and nerve exam checks strength, balance, speech, and memory. A biopsy or surgery takes some tumor to study. Gene tests on the tumor help name the exact type. A brain wave test can help if you had seizures. Sometimes a needle in the lower back takes a little spinal fluid.

What the grade means

Next up, the grade. Most brain tumors are not staged like other cancers. That is because they rarely spread outside the brain. Instead, doctors use a grade from 1 to 4. The grade tells how fast the tumor is likely to grow. Gene test results can change the grade. For cancer that spread to the brain, the first cancer matters most. The grade helps your team plan treatment. It helps all your doctors speak the same language. Ask your team what your grade means for you.

Gene tests on the tumor

Before we move to treatment, there are some things to know. Brain tumors are now named partly by their gene changes. Two tumors can look the same under a microscope. Yet they can act very differently. Gene tests help predict how a tumor will behave. They can also show which treatments may work best. There are different markers, and each has a different role. Your doctor will tell you which ones you have and what they mean. You can read more in the guide. The Questions to ask page can help too.

Main treatments

Now let's talk about treatment. Surgery removes as much tumor as is safe. Radiation uses strong beams aimed at the tumor area. Very focused radiation can treat small spots in one or a few visits. Chemotherapy medicines kill cancer cells, and some come as pills. Targeted medicines block a specific gene change. Steroids lower swelling and can ease headaches quickly. Seizure medicine helps if you have had a seizure. Some slow tumors are just watched with scans. Clinical trials are research studies that may offer new options. Ask your team about them.

Side effects and help

Let's look at side effects. Feeling very tired is common. Short walks and rest breaks help. Steroids can affect sleep, hunger, and mood. Never stop them suddenly on your own. Take seizure medicine every day, even when you feel fine. Memory and focus can change. Notes and phone reminders can help. Hair may thin where radiation goes in. Mood can change too, and there is help for that. Tell your team about any headache that gets worse. We have a whole side effects guide on this site.

Living well day to day

Now let's talk about living well. You will have regular MRI scans. A scan can look worse after radiation. That does not always mean growth. Rehab therapists can help with strength, balance, and speech. Ask your team when it is safe to drive again. Families and caregivers need support too. Talk early about your goals and wishes. Call right away for a seizure. Call for a sudden severe headache. Call for new weakness on one side. If it feels very bad, call 911. Also visit our new Screening, prevention and survivorship section.

You did great today. Thank you for learning with me. Write down your questions and bring them to your next visit. A caregiver can help you remember too. You can call your care team any time. You are not alone in this.

Call your care team right away if you have

A seizure, especially a first one, one that lasts more than 5 minutes, or seizures back to back
Sudden severe headache, or a headache with vomiting
New weakness, numbness, or drooping on one side of the face or body
New trouble speaking, understanding, or seeing
New confusion, extreme sleepiness, or hard to wake up
Fever of 100.4 F (38 C) or higher, or chills, during chemotherapy
Unusual bleeding or bruising
Swelling or pain in one leg, or sudden shortness of breath or chest pain
Redness, swelling, or fluid leaking from your surgery cut
Running out of, or being unable to take, your seizure medicine or steroids
If it feels very bad, call 911.

Side effects: what helps

Sources

Quick answers

What is brain tumors?: A brain tumor is a growth of abnormal cells in or near the brain. Some brain tumors are cancer and some are not. Even a tumor that is not cancer can cause problems, because the skull has little room to spare. A primary brain tumor starts in the brain. The most common ones in adults are meningiomas and gliomas. A glioma starts in the support cells of the brain, called glial cells. Glioblastoma is the most common fast-growing primary brain cancer in adults.
When should I call my care team?: A seizure, especially a first one, one that lasts more than 5 minutes, or seizures back to back; Sudden severe headache, or a headache with vomiting; New weakness, numbness, or drooping on one side of the face or body; New trouble speaking, understanding, or seeing; New confusion, extreme sleepiness, or hard to wake up; Fever of 100.4 F (38 C) or higher, or chills, during chemotherapy; Unusual bleeding or bruising; Swelling or pain in one leg, or sudden shortness of breath or chest pain; Redness, swelling, or fluid leaking from your surgery cut; Running out of, or being unable to take, your seizure medicine or steroids; If it feels very bad, call 911.

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.