Brain Tumors

by National Cancer Institute

Primary and Secondary Brain Tumors

A tumor that begins in the brain is called a primary brain tumor. In children, most brain tumors are primary tumors. In adults, most tumors in the brain have spread there from the lung, breast, or other parts of the body. When this happens, the disease is not brain cancer. The tumor in the brain is a secondary tumor. It is named for the organ or the tissue in which it began.

Treatment for secondary brain tumors depends on where the cancer started and the extent of the disease.

The Brain

The brain is a soft, spongy mass of tissue. It is protected by the bones of the skull and three thin membranes called meninges. Watery fluid called cerebrospinal fluid cushions the brain. This fluid flows through spaces between the meninges and through spaces within the brain called ventricles.

The brain and nearby structures

A network of nerves carries messages back and forth between the brain and the rest of the body. Some nerves go directly from the brain to the eyes, ears, and other parts of the head. Other nerves run through the spinal cord to connect the brain with the other parts of the body. Within the brain and spinal cord, glial cells surround nerve cells and hold them in place.

The brain directs the things we choose to do (like walking and talking) and the things our body does without thinking (like breathing). The brain is also in charge of our senses (sight, hearing, touch, taste, and smell), memory, emotions, and personality.

The three major parts of the brain control different activities:

Cerebrum — The cerebrum is the largest part of the brain. It is at the top of the brain. It uses information from our senses to tell us what is going on around us and tells our body how to respond. It controls reading, thinking, learning, speech, and emotions.

The cerebrum is divided into the left and right cerebral hemispheres, which control separate activities. The right hemisphere controls the muscles on the left side of the body. The left hemisphere controls the muscles on the right side of the body.

Cerebellum — The cerebellum is under the cerebrum at the back of the brain. The cerebellum controls balance and complex actions like walking and talking.

Brain Stem — The brain stem connects the brain with the spinal cord. It controls hunger and thirst. It also controls breathing, body temperature, blood pressure, and other basic body functions.

Major parts of the brain

Understanding Cancer

Cancer begins in cells, the building blocks that make up tissues. Tissues make up the organs of the body.

Normally, cells grow and divide to form new cells as the body needs them. When cells grow old, they die, and new cells take their place.

Sometimes this orderly process goes wrong. New cells form when the body does not need them, and old cells do not die when they should. These extra cells can form a mass of tissue called a growth or tumor.

Benign and Malignant Brain Tumors

Brain tumors can be benign or malignant:

Benign brain tumors do not contain cancer cells:

• Usually, benign tumors can be removed, and they seldom grow back.

• The border or edge of a benign brain tumor can be clearly seen. Cells from benign tumors do not invade tissues around them or spread to other parts of the body. However, benign tumors can press on sensitive areas of the brain and cause serious health problems.

• Unlike benign tumors in most other parts of the body, benign brain tumors are sometimes life threatening.

• Very rarely, a benign brain tumor may become malignant.

Malignant brain tumors contain cancer cells:

• Malignant brain tumors are generally more serious and often are life threatening.

• They are likely to grow rapidly and crowd or invade the surrounding healthy brain tissue.

• Very rarely, cancer cells may break away from a malignant brain tumor and spread to other parts of the brain, to the spinal cord, or even to other parts of the body. The spread of cancer is called metastasis.

• Sometimes, a malignant tumor does not extend into healthy tissue. The tumor may be contained within a layer of tissue. Or the bones of the skull or another structure in the head may confine it. This kind of tumor is called encapsulated.

Tumor Grade

Doctors sometimes group brain tumors by grade - from low grade (grade I) to high grade (grade IV). The grade of a tumor refers to the way the cells look under a microscope. Cells from high-grade tumors look more abnormal and generally grow faster than cells from low-grade tumors.

About the Author

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