Brain tumours in adults
No one knows what causes brain tumours, and there are only a few known risk factors that have been established by research. People who receive radiotherapy to the head have a higher risk of a brain tumour. Those who have certain rare genetic conditions such as neurofibromatosis - a disorder of the nervous system - or Li-Fraumeni syndrome - a condition that predisposes someone to developing cancer - are also at greater risk. However, radiotherapy and rare genetic disorders are only a factor in a small number of the approximately 4,500 new cancerous primary brain tumours diagnosed in the UK each year. Finally, age is a factor. The chance of developing brain cancer is greater in those people over the age of 65 than in people younger than 65.
A primary brain tumour is one that originates in the brain. It is not the same as cancer that develops elsewhere in the body and then spreads to the brain. Those are called metastatic tumours, and their treatment and prognosis depend on the type of cancer it is.
Not all primary brain tumours are cancerous. Approximately 4,500 of the 8,000 new cases each year are brain cancer. The rest are benign tumours, meaning they are not aggressive and do not normally spread to surrounding tissue. However, even a benign brain tumour can be a serious, life-threatening health problem.
What is a tumour?
A tumour is an abnormal mass of tissue that's formed by an abnormal accumulation of cells. Normally, the cells in your body age, die and are replaced by new cells. With cancer and other tumours, something disrupts this cycle. New cells are made when they're not needed, and old cells don't die. As this process goes on, the tumour continues to grow as more and more cells are added to the mass.
Primary brain tumours emerge from the various cells that make up the brain and central nervous system and are named based on the kind of cell they first form in. The most common types of adult brain tumours are gliomas, the commonest type of which is called an astrocytoma. These tumours form from cells called astrocytes, which are cells that help support the nerve cells.
The second most common types of adult brain tumours are meningiomas. These form in the meninges, the thin layer of tissue that lines the brain and spinal cord and can grow from a number of different kinds of brain and spinal cord cells.
What's the difference between benign and malignant brain tumours?
Benign brain tumours are non-cancerous. Malignant primary brain tumours are cancers that originate in the brain. They typically grow faster than benign tumours and aggressively invade surrounding tissue. Although brain cancer rarely spreads to other organs, it will spread to other parts of the brain and central nervous system.