What cause Brain Tumor and how do yu get it?

Primary brain tumors begin when normal cells acquire errors (mutations) in their DNA. These mutations allow cells to grow and divide at increased rates and to continue living when healthy cells would die. The result is a mass of abnormal cells, which forms a tumor.

Explanation:

Causes and Risk Factors for Brain Cancer

The exact cause of brain cancer is unknown. However, factors that can increase your risk of brain cancer include exposure to high doses of ionizing radiation and a family history of brain cancer. Cancer in another part of your body is also a risk factor.