Adult brain tumours
Brain tumors arise from the normal constituents of the brain and its coverings (meninges). Spinal tumors are considered separately.
As a general rule, brain tumors increase in frequency with age, with individual exceptions (e.g. pilocytic astrocytoma, the vast majority of which are found in young patients), and a number of uncommon tumors found in infancy (see brain tumors of infancy). There are few gender differences, except that as a general rule, gliomas are more frequent in men and meningiomas are more frequent in women.
There are numerous individual tumor entities which come under the umbrella term "brain tumor" (see WHO Classification of CNS tumors). They can broadly be divided into:
- neuroepithelial (50%)*
- meningioma (15%)
- metastases (15%)
- pituitary tumors (8%)
- vestibular schwannoma (8%)
- primary CNS lymphoma (2.5%)
- pineal tumors
- intracranial germ cell tumors 0.4% to 3.4% (around the pineal, third ventricle or suprasellar region)
* N.B. figures vary widely depending on the study (figures quoted are mostly from AH Kaye ).
Another set of figures to ponder :
- overall incidence: 5-13 cases per 100,000
- incidence in children: 2-4 cases per 100,000
- 80% of all intracranial tumors are supratentorial
- 40% are metastases
- 70% of tumors in 1-year-olds to adolescents are in the posterior fossa