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Brain Tumors: Introduction

Brain Tumors: Introduction

What is a brain tumor?

A brain tumor is an abnormal growth of tissue in the brain.

Understanding the brain and spinal cord

The brain and spinal cord make up the central nervous system (CNS). The brain is an important organ that controls thought, memory, emotion, touch, motor skills, vision, respiration, body temperature, hunger, and many other processes that regulate our body. The spinal cord is a large bundle of nerve fibers located in the back that extends from the base of the brain to the lower back. It carries messages to and from the brain and the rest of the body.

What are the major parts of the brain?

The brain has 3 main parts:

  • Cerebrum. This is the upper (supratentorial)part of the brain. It’s composed of the right and left halves (hemispheres). Functions of the cerebrum include: initiation of movement, coordination of movement, processing of vision and hearing, judgment, reasoning, problem solving, emotions, and learning.

  • Cerebellum. This is the lower (infratentorial) part of the brain. It’s located at the back of the head. Its function is to coordinate voluntary muscle movements and to maintain posture, balance, and equilibrium.

  • Brainstem. The brainstem includes the midbrain, the pons, and the medulla. Functions of this area include: movement of the eyes and mouth, relaying sensory messages (hot, pain, loud, etc.), hunger, breathing, consciousness, cardiac function, body temperature, involuntary muscle movements, sneezing, coughing, vomiting, and swallowing.

Primary brain tumors

Location of different types of tumors
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Main types of brain tumors

There are two main types of brain tumors:

  • Primary tumor. This kind of tumor starts growing first in the brain.

  • Secondary (metastatic) tumor. This kind of tumor is from a cancer that starts in another part of the body, then spreads to the brain through the lymph system or bloodstream. 

Types of primary brain tumor

There are two types of primary brain tumors:

  • Benign tumor. This kind of tumor is not cancer. It tends to grow slowly. Most benign brain tumors don’t grow into nearby tissue. Once removed, they usually don’t grow back. A benign tumor can cause symptoms like a malignant tumor depending on their size and location in the brain.

  • Malignant tumor. This kind of tumor is cancer. It usually grows fast, and grows into nearby tissue. This can make it hard to remove fully. A malignant brain tumor very rarely can spread to other areas of the body. And it may grow back after treatment. In some cases, a brain tumor that is not cancer is called malignant because of its size and location, and the damage it can do to functions of the brain.

Primary brain tumors are named by the type of brain tissue where they’re found. The most common type of primary brain tumor is a glioma. This type begins in the supportive (glial) tissue of the brain.  Some gliomas tend to grow slowly. Others grow and spread quickly. Some types of glioma include:

  • Astrocytoma. This kind of tumor come from the small star-shaped cells called astrocytes. They can grow anywhere in the brain or spinal cord. In adults, an astrocytoma usually grows in the cerebrum. In children, they grow in the cerebellum, cerebrum, and brain stem. Most astrocytomas spread into nearby normal brain tissue and are very hard to cure with surgery. Glioblastoma is a type of astrocytoma that tends to grow very quickly. 

  • Brain stem glioma. This kind of tumor of the brain stem is more common in children than in adults. Because the brain stem controls many important functions, such as breathing and heart rate, this kind of tumor usually can’t be removed by surgery.

  • Ependymoma. This kind of tumor start in cells that line the fluid-filled spaces within the brain (ventricles). It doesn’t often grow into nearby brain tissue. This means in some cases it can be cured with surgery.

  • Oligodendroglioma. This kind of tumor start in cells that make myelin, the fatty substance that surrounds nerve cells. Like an astrocytoma, this tumor tends to spread into nearby brain tissue and is often hard to cure with surgery. 

  • Optic nerve glioma. This kind of tumor grows in or around the nerve that sends messages from the eyes to the brain. This can cause vision changes. It can also cause hormone changes, due to its location near the pituitary gland. 

Other types of primary tumors include:

  • Primitive Neuroectodermal Tumor (PNET). This kind of tumor grows more often in children. It can grow anywhere in the brain in the primitive form of nerve cells. One type is the medulloblastoma. This kind of tumor start is found in the cerebellum. They are more common in children than in adults. They tend to grow and spread quickly, but they can often be treated effectively. 

  • Tumor of the pineal gland. This kind of tumor grows in and around the pineal gland. This is a tiny organ near the center of the brain. The tumor can be slow-growing, called pineocytoma. Or it can be fast-growing, called pineoblastoma.

  • Pituitary tumor. This kind of tumor starts in the pituitary gland at the base of the brain. It is almost always benign. But it can cause serious symptoms because of its location, and because it may secrete excess hormones. 

  • Craniopharyngioma. This kind of tumor starts near the pituitary gland. It is usually slow growing. But it can cause symptoms if it presses on the pituitary gland or on nearby nerves. 

  • Schwannoma. This kind of tumor starts in myelin-making cells that surround certain nerves. It’s most common in the nerve in the inner ear that helps with balance. If it grows there, the tumor is called a vestibular schwannoma or an acoustic neuroma. This type of tumor is usually benign. 

  • Meningioma. This kind of tumor starts in the outer linings of the brain and spinal cord. It is more common in adults. Most meningiomas can be removed with surgery, but some may grow back.  

  • Primary central nervous system lymphoma. This is an aggressive, rare type of tumor that starts in lymphocytes. This is a type of immune cell. The tumor is more common in people with a disease of the immune system, such as AIDS. But it can grow in healthy people.

Types of secondary brain tumors 

A secondary brain tumor is also known as a metastatic brain tumor. This is cancer that starts in another organ and then travels to the brain. In adults, secondary brain tumors are more common than primary brain tumors. Cancer in the brain that has spread from another part of the body is not considered brain cancer. It is still the same type of cancer as where it started. For example, lung cancer that has spread to the brain is called metastatic lung cancer. These are some of the most common types of cancer that spread to the brain:

  • Lung cancer

  • Breast cancer

  • Melanoma

  • Colon cancer

  • Kidney cancer

Talk with your healthcare provider           

If you have questions about brain cancer, talk with your healthcare provider. Your healthcare provider can help you understand more about this cancer.