The causes of glioblastoma are largely unknown. While research suggests that approximately 5 percent of all glioblastomas are caused by hereditary conditions, the remaining 95 percent are not attributed to any specific cause. Glioblastoma cells have more genetic abnormalities than the cells of other types of astrocytoma brain cancer. As a result, researchers believe that several different genetic mutations are involved in the development of these cancers. These genetic mutations can be caused by: