Brain Tumors in Adults
No one knows what causes brain tumors; there are only a few known risk factors that have been established by research. People who receive radiation therapy to the head as a child have a higher risk of a brain tumor over the next 20 to 30 years. And people who have certain rare genetic conditions such as neurofibromatosis -- a disorder of the nervous system -- or Li-Fraumeni syndrome -- a condition that predisposes someone to developing cancer -- are also at higher risk. But radiation therapy or rare genetic disorders are only a factor in a small number of the approximately 35,000 new primary brain tumors diagnosed each year. And finally, age is a factor. The rate of developing brain cancer is four times the rate each year in people over the age of 65 than in people younger than 65.
A primary brain tumor is one that originates in the brain. It is not the same as cancer that develops elsewhere in the body and then spreads to the brain. Those are called metastatic tumors, and their treatment and prognosis depend on the type of cancer it is.
Not all primary brain tumors are cancer. Approximately 19,000 of the 35,000 new cases each year are brain cancer. The rest are benign tumors, meaning they are not aggressive and do not normally spread to surrounding tissue. But even a benign brain tumor can be a serious, life-threatening health problem.
What Is a Tumor?
A tumor is an abnormal mass of tissue that's formed by an abnormal accumulation of cells. Normally, the cells in your body age, die, and are replaced by new cells. With cancer and other tumors, something disrupts this cycle. New cells are made when they're not needed, and old cells don't die. As this process goes on, the tumor continues to grow as more and more cells are added to the mass.
Primary brain tumors emerge from the various cells that make up the brain and central nervous system and are named for the kind of cell they first form in. The most common types of adult brain tumors are gliomas or astrocytic tumors. These tumors form from astrocytes and other types of glial cells, which are cells that help keep nerves healthy.
The second most common types of adult brain tumors are meningeal tumors. These form in the meninges, the thin layer of tissue that lines the brain and spinal cord and can grow from a number of different kinds of brain and spinal cord cells.
What's the Difference Between Benign and Malignant Brain Tumors?
Benign brain tumors are noncancerous. Malignant primary brain tumors are cancers that originate in the brain. They typically grow faster than benign tumors and aggressively invade surrounding tissue. Although brain cancer rarely spreads to other organs, it will spread to other parts of the brain and central nervous system.
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