Are primary brain tumours benign or malignant?
Primary brain tumours arise from the support cells of the brain, the glial cells. They are therefore called gliomas or are named after the cells from which they arise, astrocytomas, oligodendrogliomas or ependymomas. Some of these tumours behave in an entirely benign fashion while others behave very aggressively. The thing that distinguishes one type from another is their rate of growth. They all infiltrate (invade) into normal brain and even the most malignant do not metastasise (except in the rarest circumstances). The simple definitions of benign / malignant cannot therefore be applied to brain tumours. We talk about low grade (grade 2), intermediate grade (grade 3) and high grade tumours (grade 4) to determine the rate of growth of a tumour and therefore its degree of malignancy. (There is a grade 1 tumour which is entirely benign but this only occurs in children) The situation is further complicated by the fact a low grade tumour may remain so for many years but then ‘change its s
