How do tumors occur in brain which is a post mitotic or terminally differentiated organ?

Answer 1

A good site which offers some definitions of the origins of brain tumors is Columbia University's Deparatment of Neurology:

http://cpmcnet.columbia.edu/dept/neuro-icu/diseases_and_conditions/tumors.html

Here is an excerpt from the page I visited:"What is a brain tumor?
A tumor, or neoplasm, is a confined mass of abnormal tissue that proliferates rapidly and without cessation. Tumors involving the central nervous system (CNS) are classified according to the type of cells and the location of the tumor. Tumors are considered primary brain tumors if they originate in the CNS, or secondary (metastatic) brain tumors if they originate elsewhere and cells of the tumor migrate to the CNS. A tumor is benign if it is slow growing, and malignant if it is rapidly growing and readily invades surrounding brain tissue. About 24,000 primary brain tumors and an even larger number of metastatic brain tumors are diagnosed each year."

It sounds as though you are wondering how a mutation causing a tumor could occur after mitosis. This would be a "somatic" mutation", (as opposed to a germline mutation, occuring in the germ cells before conception). This means that the mutation originated in the body after conception, either at the site or having traveled there from some other place in the body.

Any number of mutagens could be responsible, including radiation and toxins.

My father died from the most common type of brain tumor (glioma). He received large doses of X-radiation in his teens, to cure acne (it was during the 1930's). He and 2 of his brothers all died of cancer and they'd all had the treatment. However, there's not conclusive evidence that this caused it.

For further articles on this question, visit Medline.com. You'll find more advanced articles than the ones on, say, WebMD.