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How do brain tumors form?

Answered by: Clinton J. Baird, MD
Medical Director of Neurosurgery Services & Neurosurgeon

Despite genomic medicine’s growing body of knowledge on how tumors form on a cellular level, much remains unknown, Dr. Baird says. Scientists still do not know why the vast majority of brain tumors develop, except in the rare instances where family genetics or radiation to the brain may have played a part.

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Clinton Baird: This is a very complicated question, and in brain tumors we don’t have the answers in the same way as we have in other types of tumors or cancers in the body for example lung cancer. We know that people that have tobacco use have a much higher risk of developing lung cancer. Even though someone who never smoked can develop lung cancer, it’s much more common to develop lung cancer in the setting of smoking. In the brain, we don’t have as good of a understanding of how brain tumors form. At the cellular level, we understand the genetics of what’s going on when a brain tumor forms, if there’s different tumor suppressor genes that are knocked out and different oncogenes, these are proteins and cellular mechanisms within the cell that control the growth of cells. These will become damaged, and then the cells allow to grow out of control and this is what will cause the formation of a tumor and cancer. But we don’t understand, are unable to relate direct risk factors to the formation of a brain cancer in the vast majority of settings. There are a few unusual hereditary conditions in which people have a propensity to form malignant brain tumors. These are very rare and most people do not have any known cause of their malignant brain tumor. There are also some other situations in which someone has received radiation to the brain for another reason or for a tumor that was treated and cured or controlled with the radiation long enough that they developed what’s called a secondary brain tumor, and those are thought to be caused from the radiation itself.