What is Brain Cancer?
Brain cancer is a disease where abnormal cells grow in or around the brain, forming tumours that interfere with normal brain function.
Overview
Brain tumours may begin in the brain or central nervous system or spread to the brain from cancer elsewhere in the body. They may be non-cancerous or cancerous. Even a non-cancerous tumour can cause serious problems because of its size or location and the pressure it places on brain tissue.
A tumour’s type, grade, location and molecular features help the care team understand how it may behave and which treatments may be appropriate.
Benign and Malignant Brain Tumours
Malignant
Malignant brain tumours are cancerous tumours of the central nervous system. Their behaviour varies: some grow and infiltrate surrounding tissue quickly, while others follow a different course depending on their type, grade and molecular features.
Examples include gliomas such as astrocytoma, oligodendroglioma and glioblastoma, as well as other malignant central nervous system tumours.
Benign
Benign brain tumours are non-cancerous. Many grow more slowly and have clearer borders than malignant tumours, although their behaviour varies by tumour type and grade.
They can still cause serious or life-threatening problems if they press on or damage important brain structures. Many meningiomas, pituitary neuroendocrine tumours and vestibular schwannomas are non-cancerous, but an exact diagnosis is needed to understand how a tumour may behave and whether treatment or monitoring is required.
Primary and Secondary Brain Tumours
There are two basic kinds of brain tumours – primary brain tumours and secondary (metastatic) brain tumours.
Primary Brain Tumours
A primary brain tumour begins in the brain or another part of the central nervous system.
Secondary or Metastatic Brain Tumours
Secondary brain tumours, also known as brain metastases, are the most common tumours found in the brain in adults.
They usually spread through the bloodstream from a cancer that began elsewhere in the body.
The cancers most likely to spread to the brain are lung, breast, melanoma, kidney, and colorectal cancers. A metastasis keeps the name of the original cancer. For example, colorectal cancer that has spread to the brain is called metastatic colorectal cancer.
There are many types of brain and central nervous system tumours. They are classified using features such as where they began, how the cells look and their molecular characteristics. Examples include gliomas, meningiomas, medulloblastomas and metastatic brain tumours.
Identifying the tumour type helps guide diagnosis, treatment and follow-up.
Brain tumours can cause a wide range of signs and symptoms, depending on factors such as the tumour’s type, size and location. Possible symptoms include persistent or worsening headaches, seizures, changes in vision or speech and difficulties with balance, memory or movement.
These symptoms can have many causes, but new, persistent or concerning changes should be discussed with a doctor.
Doctors classify brain tumours by their grade, which reflects how the tumour cells look under the microscope and how aggressive the tumour is likely to be.
Pathologists assign these grades based on four main features:
- Nuclear atypia (how abnormal the cells look)
- Mitotic activity (how often cells are dividing)
- Microvascular proliferation (growth of new blood vessels)
- Necrosis (areas of dead tissue).
Grades 1–2 are called low-grade tumours, which usually grow slowly. Grades 3–4 are high-grade tumours, which are more aggressive and more likely to recur.
The World Health Organization (WHO) system is the international standard.
Grade 1
- Slow-growing tumours
- Usually not malignant
- Can sometimes be cured with surgery
Grade 2
- Relatively slow-growing tumours
- May infiltrate nearby brain tissue and return after treatment
Grade 3
- Malignant tumours
- Abnormal appearance under a microscope
- Often recur
Grade 4
- Most aggressive tumours
- Grow and spread quickly, often with new blood vessel growth and areas of necrosis (dead tissue)
Researchers do not yet know what causes most brain tumours.
In scientific studies, these factors are described as risk modifiers. A risk modifier changes the likelihood of developing a tumour but is not a direct cause.
Having a risk modifier does not mean someone will definitely develop brain cancer.
Whether you’re facing a new diagnosis or supporting a loved one, help is available. Click here to explore a range of support resources, services, and guidance to assist you through every step of the brain cancer journey.