Brain cancer is a tumour or cancerous growth in the brain. A tumour, whether in your brain or elsewhere, is a mass of cells that reproduce themselves in an uncontrolled way. Tumours can be either benign or malignant.

Benign brain tumours are abnormal collections of cells that reproduce slowly and usually remain separate from the surrounding normal brain. They grow slowly, do not spread to other parts of the brain and can usually be removed more easily than malignant tumours. Malignant tumours reproduce and grow quickly by invading normal brain tissue. Their borders are hard to distinguish from the normal brain around them. That is why it is hard to remove them completely without damaging the surrounding brain.

Both benign and malignant tumours are further broken up into different types according to the kind of cell from which the tumour develops.

Benign tumours can be divided into the following:

• chordomas: starting in embryonic cells in the spine or base of the skull nerve
• hemangioblastomas: starting in the blood vessels
• meningiomas: starting in the membrane covering the brain
• osteomas: in the skull bones
• pinealomas: in the pineal gland
• pituitary adenomas: in the pituitary gland
• schwannomas: in the cells that wrap around nerves

There are also some tumour types that can be benign in some cases or malignant in others, such as meningiomas or germ cell tumours.
This article focuses on the malignant (cancerous) brain tumours.

Brain cancers are relatively rare, but they are often deadly. The most common malignant types are called gliomas, where cells called glia (cells which help support the nerve cells) become cancerous. Glioblastoma multiforme is the most common of the gliomas. Glioblastoma multiforme and anaplastic astrocytoma are fast-growing gliomas. Oligodendroglioma, another type of glioma, is also rare, but is most often found in adults. Gliomas make up between 50% to 60% of all brain tumours (malignant and benign) in both children and adults combined.
Medullablastoma, which grows from the cells of the medulla at the base of the brain, is the most common type of brain cancer in children. It usually affects children before puberty.

Primary central nervous system (CNS) lymphomas are lymphomas that arise in the brain or spinal cord. They are treated with chemotherapy and/or radiation therapy.

Finally, sarcoma and adenocarcinoma are extremely uncommon types of brain tumour.

The exact cause of cancer is unknown. Brain cancer that originates in the brain is called a primary brain tumour. It can spread and destroy nearby parts of the brain. Cancers of the breast, lung, skin, or blood cells (leukemia or lymphoma) can also spread (metastasize) to the brain, causing metastatic brain cancer. These groups of cancer cells can then grow in a single area or in different parts of the brain.

Risk factors include:

• previous radiation to the head
• immunosuppression (e.g., taking medication to suppress the immune system, HIV/AIDS)
• exposure to vinyl chloride (a chemical used in making plastic)

Brain cancer causes symptoms when it pushes on the brain or destroys brain tissue. Symptoms depend on the size and location of the tumour as well as how quickly it grows.

Although headaches are often a symptom of brain cancer, it is important to remember that most headaches are due to less serious conditions such as migraine or tension, not cancer. Headaches caused by a brain tumour are often severe, associated with nausea and vomiting and are usually worse in the morning. They can last for extended periods of time or may "come and go."

Other symptoms include:

• dizziness
• vision changes (such as double vision)
• coordination problems
• weakness or numbness on one side of the body
• seizures
• changes in mood, senses, personality, or feelings
• memory problems
• confusion or trouble concentrating

Based on the above symptoms, your doctor may suspect brain cancer. The first step in correctly diagnosing any type of brain cancer is to undergo a computerized tomography (CT) or magnetic resonance imaging (MRI) scan. These specialized scans can detect many types of brain tumours and determine their exact location and size. However, they can't tell if the tumour is cancerous or not.

A biopsy must be done to find out whether the tumour is cancerous. In order to do this, a piece of the tumour is removed during surgery. If the tumour is too deep inside the brain, surgeons can use a technique called stereotactic biopsy or three-dimensional needle placement.

An MRI scan is used to create a 3D image of the brain, which is then used to guide a needle held in a special frame to the proper spot in the brain. Tumour cells are then drawn into the needle and collected for examination. After the biopsy sample is removed, it is analyzed using microscopes and special chemicals to determine the type of tumour. It usually takes a few days to get the results of a biopsy.

Brain tumour cells can sometimes be drawn from the cerebrospinal fluid (CSF), which is a special fluid that surrounds the brain and spinal cord. The CSF is drawn out through a thin needle inserted in the lower back under local anaesthetic – this is called a lumbar puncture.

This procedure can't be done if there's any buildup of pressure in the brain. The change in brain pressure caused by a puncture could suck some of the brain tissue down into the base of the skull, causing serious complications.