Question: what causes a brain tumour?

Isabel Pires answered on 11 Mar 2015:

Most brain cancers are cause by defects or mutations in some genes important for making sure cells divide and grow normally. These genes are called tumour suppressors, because in their normal day-to-day job they stop any attempt of the cell to become tumour-like. When some damage to the DNA occur in a normal cell, these genes will be made into proteins that can tell the cell to repair that damage and stop dividing whilst this happens. If the damage is too much to handle, these proteins will trigger a death process, so that cell will die (and only that cell), to prevent the tissue (in this case the brain) being taken over by cells that might become a cancer.

There are not that many external factors known to directly cause brain tumours, unlike the link between smoking and lung cancer, which is well known. You have probably hear in the media some people saying that using mobile phones in excess can lead to brain cancer, but the research behind it is still not sufficient to say this is the case absolutely.