A brain tumor is a growth of abnormal cells in or close to the brain. Brain tumors are the leading cause of cancer related deaths in children aged 0-14 years. An estimated 200,000 adults and 2,000 children in the United States will die from a brain tumor this year.
Many different types of brain tumors exist, depending on the cell type from which they originated, size, key mutations in their DNA, and other factors. Broadly, some brain tumors are noncancerous (benign), and some brain tumors are cancerous (malignant). Of the cancerous brain tumors, “primary” tumors start in the brain, while “secondary” brain tumors originate from a cancer that started elsewhere in the body and spread to the brain. Brain tumors rarely spread to other organs, spreading instead to other parts of the brain and central nervous system. It is difficult to predict the growth rate of a brain tumor for any given patient. Symptoms will vary based on what parts of the brain are affected by the tumor, and how patients respond to treatments.
Brain tumor treatment options depend on the subtype, as well as its size and location.
The diagnosis and classification of brain tumors is based largely on the presence or absence of specific abnormalities, or molecular markers, in the DNA of brain tumor cells. For primary brain tumors, the key molecular markers that are now central for brain tumor classification and diagnosis include:
- Abnormal DNA in the gene encoding for isocitrate dehydrogenase (IDH)
- 1p/19q status
- Chemical changes to the DNA for the MGMT gene
Secondary brain tumors typically contain a very similar set of key molecular alterations as the tumors from which they originated elsewhere in the body.