A brain tumor occurs when cells grow uncontrollably in the brain. A tumor is an abnormal growth of cells. Normally, cells divide in a regulated manner. If cells keep dividing when new cells are not needed, a mass of tissue forms; this is called a tumor. There are two types of tumors: benign and malignant. Benign tumors stay in one place, grow to a certain size, and then (as a general rule) stop. Malignant tumors do not stop growing, and pieces of them travel to other parts of the body, where they also continue to grow. Malignant tumors, called cancers, are nearly all fatal if not treated. Currently, with treatment, about half of all cancers are being cured.

Brain Tumor

Brain Tumor
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Types of Brain Tumors

There are two main types of brain tumors:

  • Primary
  • Secondary

Primary Brain Tumors

Benign tumors – these begin in brain cells and remain inside the skull. A meningioma is usually a benign brain tumor, though there is a malignant or anaplastic variant that is very aggressive. About 25% of brain tumors are meningiomas. Meningiomas are technically benign, but, because they grow inside the confined space of the skull, they can do a lot of damage before they stop growing. In this sense, they are not "benign" at all. But they do not spread to other organs or infiltrate normal tissue. In most cases they can be readily removed.

Malignant tumors – these begin in brain cells and then travel to other parts of the body, they are cancerous. An astrocytoma is a malignant brain tumor. Astrocytomas account for 50% to 60% of all brain tumors. This type of tumor arises from small, star-shaped cells in the brain called astrocytes. Astrocytes are one of several types of supporting cells in the brain called glial cells. Therefore, an astrocytoma is a type of glioma. Astrocytoma is the most common form of glioma and may occur anywhere in the brain. However, it is most commonly found in the cerebrum in adults, and in the cerebellum in children.

Secondary Brain Tumors

Malignant tumors – these begin in an organ other than the brain, but spread to the brain. They are metastatic cancers. The word "metastatic" refers to colonies of the primary tumor that have taken up residence outside the tissue where they began growing.

Other Brain Tumors

Rare types of brain tumors, such as pituitary adenomas, neuromas, spinal cord tumors, and hydatid cysts, are not covered in this report.

Anatomy, Physiology, and Pathophysiology

The brain resides in a confined space, the skull. Abnormal growth of any kind—tumor, bleeding, swelling—takes up space and therefore compresses normal structures. If the compression is localized, that part of the brain begins to malfunction. The location of the abnormality may be determined by the brain function that is no longer working properly. If the compression involves the entire brain, its blood supply is diminished, and different symptoms appear.

Who Is Affected

Primary brain tumors are the second most common cancer in children and young adults. They are the third most common cancer in people between the ages of 15 and 34, fourth at ages 35 to 54, and much less common in older adults, where metastatic tumors predominate.

Causes and Complications

Ionizing radiation, which is associated with the development of meningiomas only, and several hereditary diseases are the only known causes of brain tumors. The cause of the majority of primary brain cancers is unknown. Viruses and environmental factors may play a role. The causes of secondary brain cancers are the factors that caused the malignancy at the site of origin (e.g., in the lung or breast).

Brain tumors disrupt brain activity, generally causing a slow or rapid deterioration in activity and function. Tumors may affect anything the brain does, from memory to movement. They may even irritate the brain enough to cause a seizure. Other complications include headaches or personality changes.

This Report Covers the Following:

Risk factors – factors that increase your chances of developing a brain tumor.
Reducing your risk – steps you can take that may help decrease your risk of developing a brain tumor.
Screening – when you don't have symptoms of cancer, screening tests offer a way to determine if you are at risk for or if you have a brain tumor.
Symptoms – changes in your health that should prompt you to see your doctor for further evaluation.
Diagnosis and prognosis – the steps your doctor will take to find out if you have a brain tumor. And if you do have a tumor, the testing that will determine how far it has progressed.
Treatment – the goals and options for treatment of brain tumors.
Living with a brain tumor – one man shares his experiences with a brain tumor.
Talking with your doctor – questions to ask your doctor.
Resources – places to go for further information on brain tumors.