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. Grade of tumour correlates with 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.

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

WHO 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.

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

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

Amended November 2009