Primary versus secondary tumours, gliomas, meningiomas and glioblastoma, symptoms, the molecular revolution in classification, and treatment with surgery, radiotherapy and chemotherapy.
Neurological Disorders
Intermediate
Brain Tumours
The Editors
February 1, 2026
3 min read
In plain English
A brain tumour is an abnormal growth of cells in or around the brain. Some start in the brain (primary tumours), but more often cancers spread there from elsewhere (secondary tumours). Some brain tumours are slow-growing and benign, others like glioblastoma are aggressive. Symptoms depend on where the tumour is.
Intermediate level: Builds on the basics. Introduces the real vocabulary and the mechanisms behind it.
Concepts to know first
Primary and secondary
Primary brain tumours start in the brain or its coverings. Secondary (metastatic) tumours spread from cancers elsewhere — most often lung, breast, skin (melanoma), kidney and colon — and are more common in adults than primary tumours.
Main types
The most common primary tumour is the meningioma, which arises from the meninges covering the brain. Most are benign and slow-growing, though they can still press on the brain. Gliomas arise from glial cells or their precursors and include astrocytomas, oligodendrogliomas and ependymomas. The most common malignant primary brain tumour in adults is glioblastoma, a fast-growing glioma that infiltrates surrounding tissue. Even with full treatment, median survival is only around 15 months. Pituitary tumours are usually benign but can affect hormones and vision. In children, brain tumours are the most common solid cancers; medulloblastoma, in the cerebellum, is among the most frequent malignant types.
Symptoms
Symptoms come from pressure and local damage: headaches (often worse in the morning or when lying down, sometimes with vomiting), seizures, gradually worsening weakness or numbness, speech or vision problems, personality changes or confusion. Most headaches are not tumours, but new, persistent or worsening headaches with other neurological symptoms warrant assessment.
A molecular revolution
Brain tumours were long classified by how they looked under a microscope. The World Health Organization's 2016 and 2021 classifications incorporated molecular markers. For example, mutations in the gene IDH mark a group of gliomas with a much better outlook than glioblastoma, and loss of parts of chromosomes 1 and 19 ("1p/19q codeletion") defines oligodendroglioma. In 2024 a drug targeting mutant IDH, vorasidenib, was approved in the US for certain low-grade gliomas after a trial showed it delayed progression.
Treatment
Treatment depends on type, location and grade: surgery to remove as much tumour as safely possible (often with awake mapping near critical areas), radiotherapy (including focused techniques such as Gamma Knife radiosurgery), and chemotherapy such as temozolomide. The blood-brain barrier and the tumour's infiltrative growth make treatment hard; immunotherapies, targeted drugs and tumour-treating electric fields are among the approaches being studied.
Everyday examples & things to try
Real world
Why location matters more than size
A small tumour in the brainstem or speech area can cause serious problems, while a larger, slow-growing meningioma over the frontal lobe may cause few symptoms for years. In the brain, where a tumour sits often matters as much as what it is.
Key takeaways
- Secondary (metastatic) tumours are more common than primary ones in adults.
- Meningiomas are the most common primary tumour; glioblastoma the most common malignant one in adults.
- Classification now uses molecular markers like IDH; treatment combines surgery, radiotherapy and chemotherapy.
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