This is a great question, thank you for asking
Firstly, there are two types of tumors that can
occur in the brain: primary (a tumor that
originates in the brain) and secondary (when the
cancer has spread from somewhere else to the
Most brain tumors in children are primary tumors
whereas most brain tumors in adults are secondary.
You are right in saying that nerve cells cannot
undergo mitosis cell division, but apart from
neurons, there are other supporting cells such as
various glial cells, blood vessel cells, pituitary
gland cells, meningeal cells, and those of the
nerve sheaths and skull, and other cells that are
able to replicate in brains and so that is where
the cancer comes from.