CNS tumours: an overview
- Topic
Brain tumours are now named by both their look and their genes; even ‘benign’ ones can kill by their location.
What it is
Tumours of the CNS differ from tumours elsewhere. The WHO classification gives an integrated diagnosis that joins histology, grade and molecular findings such as IDH mutation or 1p/19q codeletion. Grades run from 1 to 4 within each tumour type. Location matters as much as biology: a low-grade tumour in the brainstem may be fatal, and even diffuse low-grade gliomas infiltrate widely. Primary CNS tumours rarely spread outside the nervous system, but they can seed along the CSF. In adults most are supratentorial; in children many arise in the posterior fossa.
Key facts
- Pituitary neuroendocrine tumours, craniopharyngioma and pineal tumours are covered with the endocrine system; schwannomas and neurofibromas with peripheral nerve.
- Clinical signs come from raised pressure (headache, vomiting, papilledema), seizures and focal deficits.
The main CNS tumours at a glance
| Tumour | Typical age | Typical site | Molecular marker |
|---|---|---|---|
| Glioblastoma, IDH-wildtype | Older adults | Cerebral hemispheres, crosses corpus callosum | EGFR amplification, TERT promoter, +7/−10 |
| Astrocytoma, IDH-mutant | Young adults | Hemispheres, frontal | IDH1/2, ATRX loss, TP53 |
| Oligodendroglioma | Adults | Frontal lobe, cortex | IDH plus 1p/19q codeletion |
| Pilocytic astrocytoma | Children, young adults | Cerebellum, optic pathway | BRAF fusion (KIAA1549-BRAF) |
| Medulloblastoma | Children | Cerebellum (vermis) | WNT, SHH, groups 3 and 4 |
| Ependymoma | Children (fourth ventricle), adults (spinal cord) | Ventricles, cord | ZFTA fusion, PFA/PFB groups, MYCN |
| Meningioma | Adults, more women | Dura | NF2 loss |
| Primary CNS lymphoma | Older adults, immunosuppressed | Periventricular | Large B cells, EBV in immunosuppression |
| Metastasis | Adults | Grey-white junction | Depends on primary |
Clinical notes
- MRI with contrast is the main imaging test; biopsy with molecular testing gives the diagnosis.
- Treatment combines surgery, radiotherapy and chemotherapy depending on type, grade and molecular profile.
Test yourself
Think of the answer, then tap the question to see it.
What is the most common tumour found in the adult brain?
Metastasis from a cancer elsewhere, most often lung, breast or melanoma.
What does an integrated diagnosis of a CNS tumour combine?
Histologic type, CNS WHO grade and molecular findings such as IDH status or 1p/19q codeletion.
How do primary brain tumours usually spread?
By local infiltration and seeding through the CSF; spread outside the CNS is rare.
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Central Nervous System Tumors Treatment (PDQ®)–Health Professional Version (National Cancer Institute, 2026).
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Representative model, for educational purposes only.