A brain tumour is a mass, or lump in the brain which is caused when brain cells divide and grow in an uncontrolled way.
What causes brain cells to start growing and dividing differently from healthy cells, forming a high grade (cancerous) or low grade (benign) tumour is not yet understood.
There are over 130 different primary brain and spinal tumours which are grouped and named according to the type of cell they grow from, their location in the brain and how quickly they are likely to grow and spread.
A brain tumour originating in the brain is known as a primary brain tumour.
If the tumour started somewhere else in the body e.g. the lung, then spread to the brain, it is known as a secondary brain tumour or metastases. There are over 130 different primary brain and spinal tumours which are grouped and named according to the type of cell they grow from, their location in the brain and how quickly they are likely to grow and spread.
Brain tumours include types of brain cancer, however not all brain tumours are cancerous.
Brain tumours are graded 1-4 by their behaviour such as speed of growth and how likely they are to spread. These grades are then split into low grade (1-2) and high grade (3-4), with low grade tumours defined as non-cancerous and high grade tumours as cancerous.
Around 11,000 people are diagnosed with a primary brain tumour each year. This means that 29 people in the UK are diagnosed with a brain tumour every day. It is important to note that other conditions can cause similar signs or symptoms of brain tumours, but it is important to recognise these, so you can go to your doctor if you are concerned.
It's important to know that these types of mutation are mistakes that are found only in the tumour cells and not in the egg or sperm cells that make up a baby. This means they will not be inherited by your children.
Very often, we don't know what will have caused your brain tumour, read more about the brain tumour risk factors we know about.
Research, including pioneering programmes funded by The Brain Tumour Charity, is gradually discovering which genes are involved in causing different types of brain tumour to develop in the first place, as well as their ongoing growth.
This will hopefully lead to discovering what causes the mistakes in the genes to happen and also to treatments that are tailored to the genetic make-up of each person's tumour.
Cells are the basic building blocks of all living things. The human body is composed of trillions of cells.
Normally, when a cell divides, it has to copy its genes to put into the new cell. However, mistakes can sometimes be made when copying the genes. These mistakes are called mutations.
Many mutations don't have any obvious effect, but if a mistake happens in a gene that helps to control how a cell grows and divides, it can cause the cell to grow uncontrollably and a tumour to grow.
Read more about brain cells and how brain tumours form.