is made up of many types of cells. Each type of cell has special functions.
Most cells in the body grow and then divide in an orderly way to form
new cells as they are needed to keep the body healthy and working
properly. When cells lose the ability to control their growth, they
divide too often and without any order. The extra cells form a mass
of tissue called a tumor. Each year, more than 16,000 people find
out they have a brain tumor. Tumors are benign or malignant.Benign
brain tumors do not contain cancer cells. Usually these tumors can
be removed, and they are not likely to recur. Benign brain tumors
have clear borders. Although they do not invade nearby tissue, they
can press on sensitive areas of the brain and cause symptoms.
Malignant brain tumors contain cancer cells. They interfere with vital
functions and are life-threatening. Malignant brain tumors are likely
to grow rapidly and crowd or invade the tissue around them. Like a
plant, these tumors may put out "roots" that grow into healthy
brain tissue. If a malignant tumor remains compact and does not have
roots, it is said to be encapsulated. When an otherwise benign tumor
is located in a vital area of the brain and interferes with vital
functions, it may be considered malignant (even though it contains
no cancer cells).