Brain tumours are classified by grade (severity) and by cell type (cell type can also be indicative of location). This website focuses on the most common type of primary brain tumours, gliomas, but much of the information is also very relevant to other rare types of brain cancer. Secondary brain cancers – spread from a cancer that started in another part of the body – can be quite different from primary brain cancers so please check any information with your healthcare team.
The main cell types are:
- Glioblastoma multiforme (grade IV)
- Astrocytomas: astrocytes (low grade and high grade)
- Oligodendrogliomas: oligodendrocytes (low grade and high grade)
- Ependymomas: ependymal cells (low grade and high grade)
- Brainstem glioma: develop in the brain stem
- Optic nerve glioma: develop in or around the optic nerve
- Mixed gliomas, such as oligoastrocytomas, contain cells from different origins
The main grades are:
- Grade 1 gliomas [Grade I]
- Lower grade gliomas [Grade II and III]
- Glioblastoma [Grades IV]
Note
The World Health Organization (WHO) sponsors a group of pathologists and clinicians who are experts in brain and spinal cord tumours to develop the criteria for how brain tumours are classified and graded. They periodically review and update new recommendations that guide the WHO’s brain tumour classifications. As of 2021, grade classifications of brain tumours were updated.
Key takeaways from the WHO classification updates
• There will now be grading within tumor types, rather than across different tumour types (e.g. if you are diagnosed with an oligodendroglioma, you will now also be given a specific grade of 2 or 3).
• There will now be a division of diffuse gliomas into groups that occur primarily in adults:
– Astrocytoma, IDH-mutant (grades 2 through 4)
– Oligodendroglioma, IDH-mutant and 1p/19q-co-deleted (grades 2 and 3)
– Glioblastoma, IDH-wildtype (grade 4)
• As CNS tumor grading still differs from other tumor grading systems, WHO CNS5 endorses use of the term “CNS WHO grade” when assigning grades.
How does this affect you if you have been previously diagnosed under the former WHO classification?
It’s important to note that while the terminology used to classify certain tumor types may change to more accurately describe its molecular features, in most cases, these updates will not impact your treatment or quality of care. If you have any questions or concerns about how your care and treatment plans may be impacted, consult your cancer care team, who should be aware of the new classification. You may consider asking questions such as:
– Should I have my tumor tissue tested to determine if it should be reclassified?
– Is there any tumor tissue left from my initial biopsy and diagnosis that can be retested?
If you would like to do read further reading on the WHO classification of tumours, please visit this summary.
Grade 1 gliomas
Grade I gliomas are usually low risk and can be removed surgically depending on their location.
Lower grade gliomas
Lower grade gliomas are can range from the well-differentiated to less differentiated (grade III);. However, they can recur and increase in grade overtime. Click here for more information about lower grade gliomas.
Glioblastoma
Grade IV glioblastoma are the most undifferentiated; these are malignant, more aggressive and carry a worse prognosis. Click here for more information about high grade gliomas.