Question

If neurons dont multiply how do v get brain cancer?

Answer 1

You are right that cancer is due to rapid division of cells, that neurons don't usually divide after the brain forms, and that the brain has more cell types than just neurons.

Brain cancer can come from cells other than neurons.

For example, glial cells support neurons and help them work. They can become cancer cells.

Answer 2

Apart from neurons, there are several other types of supporting cells, including various glial cells, blood vessel cells, pitutary gland cells, meningeal cells and those of the nerve sheaths and skull, which retain capability to replicate in adult mammalian brain, thus almost all tumors in adult people arise from these lineages.

Only a fraction of brain tumors are of neuronal origin, usually arising in embryonic or foetal stages of the children or occasionally in neonatal life, when the neurons continue to divide at low rate.However, about 10 to 15 % of the brain neoplasms are metastases from primary tumors in other body sites than brain.