Tumors of the Central Nervous System (CNS) are masses of abnormal cells in the brain that have grown out of control. In most other parts of the body, it is very important to distinguish between benign and malignant tumors. Benign tumors do not grow into nearby tissues or spread to distant areas, so in other parts of the body are almost never life threatening. One of the main reasons that malignant tumors are so dangerous is that they can spread throughout the body. Although tumors of the nervous system rarely spread to other parts of the body, instead most of these can be spread through brain tissue. Even so-called benign tumors can, as they grow, cause pressure and destroy normal brain tissue, causing damage that often results in disability and sometimes death.
Tumors that originate in the brain (primary tumors) are not the same as those tumors that start in other organs and then spread to the brain (metastatic tumors or secondary tumors). In adults, metastatic nervous system tumors are in reality, more common than primary. Primary tumors of the nervous system can begin in almost any tissue or cell type within the brain or spinal cord. Some tumors have a combination of cell types.
Gliomas are a group of tumors that start in glial cells. Several tumors can be considered gliomas, including glioblastoma (also known as glioblastoma multiforme), astrocytomas, oligodendrogliomas, and ependymomas. About three in 10 of all brain tumors are gliomas. Gliomas are brain tumors that grow faster.
Meningiomas arise from the meninges (the layers of tissue that surround the outside of the brain and spinal cord). About one in three primary brain tumors and spinal cord tumors are meningiomas. These are the most common brain tumor in adults.