A glioma is a type of brain tumor that forms from glial cells. These cells support and protect neurons in the brain. There are many types and subdivisions of gliomas.

Gliomas are the most common type of brain tumor in adults, making up around 78% of cancerous brain tumors.

Types of gliomas include astrocytomas and ependymomas.

This article will explain what a glioma is and the outlook for a person with a glioma diagnosis. It will also explain types, risk factors, and treatment options for glioma.

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A glioma is a type of brain tumor that starts growing in the glial cells.

Glial cells protect and support neurons, holding them in place and allowing them to function correctly. They provide the nerve cells with oxygen and nutrients and remove dead cells from the brain.

Not all gliomas are cancerous. Sometimes the cells do not reproduce and spread.

Low-grade gliomas spread slowly, and high-grade gliomas spread more quickly.

The outlook for a person with glioma depends on different factors. For example, the outlook can change with the type of glioma a person has, or depending on their age.

The American Cancer Society provides the following five-year survival rates for different types of glioma, depending on a person’s age:

Tumor typeAge 20–44Age 45–54Age 55–64
Low-grade (diffuse) astrocytoma73%46%26%
Anaplastic astrocytoma58%29%15%
Anaplastic oligodendroglioma76%67%45%
Ependymoma/anaplastic ependymoma92%90%87%

There are three types of gliomas.


Some brain tumors grow from star-shaped glial cells called astrocytes. These tumors are astrocytomas.

Grade I astrocytomas are called pilocytic astrocytomas. They tend to be slow-growing and have well-defined borders.

Grade IIs are known as low-grade astrocytomas or diffuse astrocytomas. They are slow-growing but do not have well-defined borders. They are common among people aged 20–50.

Grade III astrocytomas are also called anaplastic astrocytomas. They account for 2% of all brain tumors and grow faster and more aggressively than lower-grade tumors. They also grow into the surrounding tissue.

Grade IV astrocytomas are called glioblastomas or GBMs. They are the most aggressive type of glioma. This is the most common high-grade brain tumor occurring in adults. GBMs account for 12–15% of all brain tumors and have a 5-year survival rate of around 4%.

Learn more about glioblastomas here.


Brain tumors that occur in ependymal cells are called ependymomas. They are quite rare in adults, making up around 2–3% of primary brain tumors.

Grade I ependymomas are usually slow-growing and may either be subependymomas or myxopapillary ependymomas.

Grade II ependymal tumors are the most common and are simply known as ependymomas. However, doctors may further categorize them as cellular, papillary, clear cell, or tancytic ependymomas.

Grade III ependymomas are faster-growing tumors known as anaplastic ependymomas.


Brain tumors that develop from oligodendrocytes are called oligodendrogliomas.

Grade II oligodendrogliomas are low grade, and Grade III or anaplastic oligodendrogliomas are high grade.

Learn more about types of brain cancer here.

The symptoms of gliomas vary depending on a number of factors. They depend on the size of the tumor as well as the location in the brain or spinal cord where the tumor develops.

The most common symptom of a brain tumor is headaches, which occur in 35% of people with brain tumors.

Other common symptoms of brain tumors may include:

Learn about early symptoms of brain cancer here.

Risk factors are things that can increase the likelihood that a person develops an illness or disease.

However, most brain tumors have unknown causes. They do not have links to anything that a person could have prevented.

Hereditary factors

Some genetic disorders might lead to an increased risk of malignant brain tumors. Such genetic disorders may include:

  • neurofibromatosis type 1
  • neurofibromatosis type 2
  • von Hippel-Lindau syndrome
  • Li-Fraumeni syndrome

However, only around 5% of people with brain tumors have any of the above genetic conditions.

Environmental factors

Certain substances that a person may encounter in the workplace could lead to cancer.

For example, exposure to vinyl chloride may increase a person’s risk of developing glioma. However, researchers have not found a direct link.

If a person shows signs or symptoms that may relate to a glioma, their healthcare professional may discuss their medical history and carry out a neurological exam.

A doctor may use imaging scans or a biopsy to diagnose glioma.

Imaging scans that may be able to help a doctor determine if a tumor is present include:

These scans cannot confirm the type of cells that form the tumor. In this case, a doctor may recommend a biopsy.

When treating brain tumors, doctors try to remove as much of the tumor as possible and prevent it from recurring. They also have to be very careful not to damage the healthy parts of the brain.

According to the National Cancer Institute, there are five types of standard treatment:

Active surveillance

This is where a person has regular checkups to ensure that their condition does not get worse. They do not receive actual treatment.

Active surveillance can be helpful for people with tumors that are very slow-growing and are not causing any symptoms.

Risks or potential side effects of treatment might outweigh the benefits at this stage, so doctors may watch the person’s condition for a period of time before treatment.


Surgery may be the first step in treating glioma. Depending on the grade of the tumor, a surgeon may successfully remove the whole tumor, or a great deal of cancerous tissue.

Depending on where the tumor is in the brain and the functions it affects, it may not be possible to remove the whole tumor.

Partially removing the tumor can decrease swelling in the brain and alleviate some of the symptoms.

Radiation therapy

External beam radiation therapy, or EBRT, is a type of radiation therapy doctors use to treat gliomas.

A large machine delivers high-energy rays (such as X-rays, photons, or protons) into a person’s body, to the tumor.


Chemotherapy uses drugs to stop cancer cells from growing.

Systemic chemotherapy is when the drugs enter the bloodstream and travel around the body. A subset of chemotherapy drugs can cross the blood-brain barrier to target gliomas.

For brain tumors, doctors may recommend the use of a dissolvable wafer that they place directly in the brain at the tumor site after removing the tumor.

This method is called localized chemotherapy. It helps target any potential remaining tumor and may avoid unwanted side effects in other parts of the body.

Learn the difference between chemotherapy and radiotherapy here.

Targeted therapy

Targeted therapies specifically affect certain molecules that cancer cells require to grow and thrive.

One such therapy is a drug called bevacizumab, which the National Comprehensive Cancer Network recommends. This drug impairs the growth of cancer cells by starving the blood supply the cancer cells require to survive.

The outlook for a glioma depends on different factors. A person should contact their doctor to determine the outlook for their specific case.

If a person suspects that they have a glioma, they should visit their doctor as soon as possible to confirm or rule it out.