A brain tumour is a growth of cells multiplying in an abnormal, uncontrollable way in the brain.
There are different types of brain tumour, depending on the type of brain cells they have grown from. More than half of all brain tumours are gliomas.
Brain tumours are also graded from 1 to 4 according to their behaviour, such as how fast they grow and how likely they are to spread.
Low-grade brain tumours
Generally, low-grade brain tumours - grades 1 or 2 - are slow growing and unlikely to spread. They are usually benign (non-cancerous), which means they tend to stay in one place and do not invade other areas of the brain or spread to other parts of the body.
However, low-grade gliomas will frequently grow back after treatment. More seriously, they can also mutate (change) into high-grade tumours (grade 3 or 4), which are fast-growing cancerous tumours that are likely to spread. About half of all low-grade glioma tumours mutate in this way within five years of diagnosis.
If you have been diagnosed with a low-grade brain tumour, your treatment will depend on the type and location of the tumour. Your outlook will depend on whether it grows back and whether it mutates.
Main types of low-grade brain tumour
- Gliomas: these are tumours of the glial tissue, the tissue that binds nerve cells and fibres together. The majority of brain tumours are gliomas.
- Meningiomas: these are (usually non-cancerous) tumours of the membranes that cover the brain.
- Acoustic neuromas: these tumours grow in the acoustic nerve, which helps to control your hearing and balance.
- Craniopharyngiomas: these are tumours that grow near the base of the brain and are most often diagnosed in children, teenagers and young adults.
- Haemangiomas: these are tumours of the brain's blood vessels, which can cause seizures and partial paralysis.
- Pituitary adenomas: these are tumours of the pituitary glands (pea-sized glands below the brain).
Mixed brain tumours
Mixed brain tumours are made up of two or more different types of tumours, sometimes of different grades.
For example, a mixed brain tumour may be a combination of a high-grade astrocytoma (a tumour of the cells thought to provide the brain's framework) and a low-grade or benign oligiodendroglioma (a tumour of the cells that produce the fatty covering of nerves).
If you have been diagnosed with a mixed-grade brain tumour, you will be treated for the most aggressive part of the tumour. Your outlook will depend on how much of the tumour is high-grade (malignant), the location of the tumour in your brain, and other factors such as your general health.
Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.
