Cancer InDepth: Brain Tumors
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.
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Types of Brain Tumors
There are two main types of brain tumors:
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:
Last reviewedSeptember 2009by Mohei Abouzied, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.