Brain tumours are graded by the World Health Organisation (WHO) from 1 – 4, according to how they behave i.e. how fast they grow and how likely they are to spread within the brain.
Tumours graded 1 and 2 are slow-growing, and are sometimes referred to as ‘benign’ or low grade. The word ‘benign’ is used less nowadays as it is not thought to be helpful in describing the tumour, as these low grade tumours are still serious.
Tumours graded 3 and 4 are fast-growing, more aggressive tumours, sometimes referred to as ‘malignant’ or ‘cancerous’, meaning they are more likely to get bigger more quickly and sometimes spread to other parts of the brain or spinal cord.