There are more than 100 different types of brain tumour, depending on which cells within the brain are involved. The most common (about 50 per cent of brain cancers) is called a glioma, and it is formed not from the nerve cells of the brain but from the glial cells, which support those nerves. The most aggressive form of glioma is known as a glioblastoma multiforme these tumours form branches like a tree reaching out through the brain and may be impossible to completely remove.
Other tumours include:
Meningiomas - account for about a quarter of brain cancers and are formed from cells in the membranes, or meninges, that cover the brain
Pituitary adenomas - tumours of the hormone-producing pituitary gland
Acoustic neuromas - typically slow-growing tumours of the hearing nerve often found in older people
Craniopharyngioma and ependymomas - often found in younger people
The treatment and outlook for these different brain tumours varies hugely. Some, such as meningiomas and pituitary tumours, are usually (but not always) benign, which means they don't spread through the brain or elsewhere in the body. However, they can still cause problems as they expand within the skull, compressing vital parts of the brain. Other types of brain cancer are malignant, spreading through the tissues and returning after treatment.
Brain tumours are also graded in terms of how aggressive, abnormal or fast-growing the cells are. Exactly where the tumour forms is also critical, as some areas of the brain are much easier to operate on than others, where important structures are packed closely together.
The type of treatment offered and the likely response depends on the type, grade and location of the tumour. Unlike many other organs, it's very difficult to remove…