Definition of Brain tumor - primary - adults:

A primary brain tumor is a group (mass) of abnormal cells that start in the brain. This article focuses on primary brain tumors in adults.

See also:

• Brain tumor - metastatic (cancer that has spread to the brain from elsewhere in the body)
• Brain tumor - children

Causes, incidence, and risk factors:

Primary brain tumors include any tumor that starts in the brain. Primary brain tumors can arise from the brain cells, the membranes around the brain (meninges), nerves, or glands.

Tumors can directly destroy brain cells. They can also damage cells by producing inflammation, placing pressure on other parts of the brain, and increasing pressure within the skull.

The cause of primary brain tumors is unknown. There are many possible risk factors that could play a role.

• Radiation therapy to the brain, used to treat brain cancers, increases the risk for brain tumors up to 20 or 30 years afterwards.
• Exposure to radiation at work or to power lines, as well as head injuries, smoking, and hormone replacement therapy have NOT yet been shown to be factors.
• The risk of using cell phones is hotly debated. However, most recent studies have found that cell phones, cordless phones, and wireless devices are safe and do not increase the risk.
• Some inherited conditions increase the risk of brain tumors, including neurofibromatosis, Von Hippel-Lindau syndrome, Li-Fraumeni syndrome, and Turcot syndrome.

SPECIFIC TUMOR TYPES

Brain tumors are classified depending on the exact site of the tumor, the type of tissue involved, whether they are noncancerous (benign) or cancerous (malignant), and other factors. Sometimes, tumors that start out being less invasive can become more invasive.

Tumors may occur at any age, but many types of tumors are most common in a certain age group. In adults, gliomas and meningiomas are most common.

Gliomas come from glial cells such as astrocytes, oligodendrocytes, and ependymal cells. The gliomas are divided into three types:

• Astrocytic tumors include astrocytomas (less malignant), anaplastic astrocytomas, and glioblastomas (most malignant).
• Oligodendroglial tumors also can vary from less malignant to very malignant. Some primary brain tumors are made up of both astrocytic and oligodendrocytic tumors. These are called mixed gliomas.
• Glioblastomas are the most aggressive type of primary brain tumor.

Meningiomas are another type of brain tumor. These tumors:

• Occur most commonly between the ages of 40 - 70
• Are much more common in women
• Are usually (90% of the time) benign, but still may cause devastating complications and death due to their size or location. Some are cancerous and aggressive.

Other primary brain tumors in adults are rare. These include:

• Ependymomas
• Craniopharyngiomas
• Pituitary tumors
• Primary lymphoma of the brain
• Pineal gland tumors
• Primary germ cell tumors of the brain