Disorders

What is a brain tumor?

Reviewed May 2026 by Katy Peters, MD, PhD, FAAN

Definition: A brain tumor is a mass or growth of abnormal cells in the brain or nearby tissue. Some brain tumors are noncancerous (benign), while others are cancerous (malignant).

Doctors often describe brain tumors as:

  • Primary tumors, which begin in the brain
  • Secondary (metastatic) tumors, which start as cancer in another part of the body and spread to the brain

There are more than 100 types of brain tumors. Each type can behave differently, which is one reason treatment plans are tailored to each person.

Brain tumors can affect people in different ways. Learning the tumor type, where it’s located, and how it’s affecting the brain can help you and your care team make informed decisions about prognosis (what you can expect in the future), treatment, and next steps. 

What are the symptoms of a brain tumor?

Symptoms can vary depending on the tumor’s type, size, and location in the brain. Some symptoms start gradually, while others are more noticeable right away.

Common symptoms may include:

  • New onset or worsening headaches
  • New onset seizures
  • Nausea or vomiting
  • Changes in vision, hearing, or speech
  • Trouble with balance or coordination
  • Weakness or numbness in parts of the body
  • Changes in memory, mood, or personality

Some symptoms can be easy to miss at first. If something feels different or concerning, it’s worth talking with a medical provider or neurologist.

What causes brain tumors and what are the risk factors?

Doctors don’t always know exactly what causes a brain tumor. A primary brain tumor begins when cells in the brain develop changes that make them grow out of control. A secondary brain tumor happens when cancer from another part of the body spreads to the brain.

Risk factors may include:

  • Age: The risk of a brain tumor increases with age.
  • Exposure to radiation: People who have been exposed to ionizing radiation have a higher risk of brain tumors. Sources of radiation can include radiation therapy used to treat cancer. Common everyday sources such as power lines, cellphones, and microwave ovens have not been proven to cause brain tumors.
  • Family history and genetic conditions: A small number of brain tumors occur in people with a family history of brain tumors or certain inherited conditions.

How is a brain tumor diagnosed?

Medical history and exam: Your medical provider or neurologist will ask about your symptoms, your health history, and when you first noticed any changes. A neurological exam helps check how well your brain and nervous system are working.

Imaging tests: MRI (magnetic resonance imaging) is the imaging test most often used to look for a brain tumor. CT (computed tomography) scans may also help in some situations.

Biopsy: A neurosurgeon may remove a small sample of the brain tumor so it can be examined under a microscope. This evaluation can help identify the tumor type and guide initial treatment decisions.

Molecular testing: Some common tests for genetic or molecular features of the tumor are performed to determine diagnosis and treatment planning.

What treatments are available for brain tumors?

Treatment depends on the type, size, and location of the tumor, as well as your overall health. Many people receive a combination of treatments.

Common treatment options include:

  • Surgery: Safely removing as much of the tumor as possible
  • Radiation therapy: Using high-energy beams to target and kill tumor cells
  • Chemotherapy: Using medicines to kill the tumor or slow its growth
  • Targeted therapy or immunotherapy: Newer treatments that focus on specific features of the tumor

Symptomatic care

In addition to treating the underlying brain tumor, treatment of related symptoms such as seizures, headaches, changes in cognition, speech, and motor function are often needed.

Symptomatic treatment options can include:

  • Anti-seizure medications: medicines that control seizures
  • Corticosteroids: medicines that are used to control brain swelling, a common condition seen with brain tumors
  • Antiemetic agents: Used to prevent or treat nausea and vomiting
  • Physical therapy, occupational therapy, and speech therapy
  • Counseling and/or psychotherapy

Caring for and navigating brain tumor

Explore practical tips, personal stories, and expert guidance for living well with brain tumor.

Frequently asked questions

Are all brain tumors cancerous?

No. Many brain tumors are noncancerous (benign), but even noncancerous tumors can affect important parts of the brain and cause symptoms. Cancerous (malignant) tumors may grow more quickly and can require more aggressive treatment.

What are the side effects of brain tumor treatment?

Side effects vary depending on the treatment, but may include:

  • Fatigue
  • Nausea
  • Hair loss (with radiation and some chemotherapies)
  • Changes in memory or concentration
  • Weakness or other neurological changes

Some side effects improve over time, while others may last longer. Your neurology care team can help you manage them and talk through what to expect.

Can brain tumors come back after treatment?

In some cases, the tumor can come back. This is called recurrence. The chance of a tumor coming back depends on the type of tumor and how it was treated. Ongoing follow-up care and imaging help your care team watch for changes over time.

What factors can affect outlook after a brain tumor diagnosis?

Outlook can vary widely. Some tumors respond well to treatment, while others can be more complex. Your care team can help you understand what to expect based on your specific situation.

Factors that can affect outlook include:

  • Tumor type and how aggressive it is
  • Location in the brain
  • How well you’re able to function
  • Age and overall health
  • How much tumor can be removed
  • Genetic and molecular characteristics