World Health Organisation (WHO) classification of brain tumours

Unlike other cancers where grade can vary depending on how aggressive cancer cells look under the microscope, most brain tumours can be given a grade based on the diagnosis. So for example Pilocytic astrocytoma is always a grade I and a Glioblastoma is always grade IV. The exception to this rule is Meningiomas – they can be grade I, II or III. The grade of tumour correlates with tumour behaviour. Grade I tumours are more benign in their nature and can on occasion be cured by surgery; grade IV tumours are most commonly highly malignant and fatal.

Grade I – includes tumours that grow slowly and are often removable and curable with surgery.

Grade II – includes tumours that tend to spread and recur more after treatment than grade I tumours. Most of these tumours will in due course transform into high grade brain tumours with a poor prognosis.

Grade III – these tumours behave quite aggressively and tend to spread into surrounding brain tissue quite easily.

Grade IV – these are the most aggressive malignant tumours, they often progress rapidly and have a poor prognosis.