If cancer occurs only in dividing cells, how can the brain develop cancer even though all brain cells are differentiated and don't divide?

Explanation:

Cancer occurs in dividing cells only because genetic materials divide into two equal portions during division. This process may be interrupted by carcinogenes or mutagenes to make mutate cells and then render them as cancer cells. In the brain, the cells are differentiated and there is no chance to start division, then how can cancer be found in the brain.