In our brains and spinal cords, different cells have different jobs. It is the job of glial cells to support the other cells. When a tumour is created in the glial cells it is called a glioma. There are different types of glial cells (supporting cells). Oligodendrocyte cells are types of glial cells. An Oligodendroglioma then is a tumour that has been made from Oligodendrocyte cells.