Glioma
Gliomas are cancerous brain tumours that start in glial cells. These are the supporting cells of the brain and the spinal cord. Some types of gliomas grow faster than others.
Types of glioma
There are different types of gliomas. To decide on your type of glioma, an expert (pathologist) looks at a sample of your brain tumour. They look at:
- the type of glial cell it started in – there are different types of glial cells, for example, astrocytes and oligodendroctyes
- changes to genes and proteins in the cells – for example the IDH gene
They also look at how normal or abnormal the tumour cells look (the grade). The more normal the cells look, the lower the grade. The more abnormal the cells look, the higher the grade.
Doctors use a system for classifying brain tumours into groups and types. This system is regularly updated. The latest is the World Health Organisation (WHO) classification of 2021.
Based on the 2021 WHO classification, the 3 main types of glioma in adults are:
- astrocytoma, IDH mutant
- oligodendroglioma, IDH mutant
- glioblastoma, IDH wildtype
There are some gliomas which are more common in children. Doctors group (classify) these together and call them child (paediatric) type gliomas. Adults can sometimes get these tumours.
Other rare types of glioma in adults include:
- diffuse midline glioma
- diffuse hemispheric glioma
- pilocytic astrocytoma
Astrocytoma
Astrocytoma is the most common type of glioma. It develops from a type of glial cell called an astrocyte. There are different types of astrocytoma.
Doctors have changed the way they describe and group astrocytomas. All astrocytomas are now called:
- astrocytoma, IDH mutant
There are 3 grades of IDH mutant astrocytomas, based on how quickly they are likely to grow:
- grade 2 (doctors sometimes call these diffuse)
- grade 3 (doctors sometimes call these anaplastic)
- grade 4
Oligodendroglioma
Oligodendrogliomas are a rare type of glioma. They develop from glial cells called oligodendrocytes.
You might hear your tumour described as:
- oligodendroglioma, IDH mutant, and 1p/19q codeleted
Doctors put oligodendrogliomas into groups based on how quickly they are likely to grow. This is the grade. They can be:
- grade 2 (doctors sometimes call these diffuse)
- grade 3 (doctors sometimes call these anaplastic)
Grade 3 is the highest grade for oligodendrogliomas.
Glioblastoma
Glioblastoma is a type of fast growing (high grade) glioma. In the past it was also called glioblastoma multiforme or GBM. Doctors have changed how they name glioblastoma. You might now hear it described as:
- glioblastoma, IDH wildtype
All glioblastomas are grade 4.
What are diffuse and anaplastic gliomas?
The World Health Organisation (WHO) no longer use the terms anaplastic or diffuse when describing the different types of brain tumour. But you might still hear or read these terms.
Most gliomas are diffuse. This means they don’t have a clear boundary between the tumour and normal brain tissue. Doctors class most grade 2 gliomas as diffuse.
Anaplastic means the cancer cells divide rapidly. They don’t look or behave like normal cells. Doctors class most grade 3 gliomas as anaplastic.
What do IDH mutant and IDH wildtype mean?
Your doctor looks to see if there are certain gene changes in the brain tumour cells. These tests are also called biomarker or molecular studies. Your doctor uses these test results to decide what type of glioma you have.
IDH (isocitrate dehydrogenase) is a gene. Your doctor looks for permanent changes (mutations) in the IDH gene, which will help predict its behaviour.
Your type of glioma will depend on whether there are changes in this gene:
- IDH mutant means you have changes (mutations) in the IDH gene
- IDH wildtype means you don’t have changes in the IDH gene (the term ‘wildtype’ describes an unchanged gene)
Brain stem glioma
Glioma in the brain stem is very rare. The brain stem is the lowest part of the brain, that connects with the spinal cord. It controls body functions that we don’t usually think about such as breathing and your heart rate.
Brain stem gliomas are more common in children than in adults. For some children, they grow rapidly and spread to other parts of the brain. Brain stem gliomas in children are also called diffuse intrinsic pontine glioma (DIPG).
Coping with glioma
Coping with a diagnosis of a brain tumour can be difficult, both practically and emotionally. It can be especially difficult when you have a rare tumour. Being well informed about the type of tumour you have, and its treatment can make it easier to cope.
