Brain Tumors

The Brain


The brain is a soft, spongy mass of tissue. It is protected by:
• The bones of the skull
• Three thin layers of tissue (meninges)
• Watery fluid (cerebrospinal fluid) that flows through spaces between the meninges and through spaces (ventricles) within the brain

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.

Brain tumors
This picture shows 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 three major parts of the brain control different activities:
  • Cerebrum: The cerebrum 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. 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 controls balance for walking and standing, and other complex actions. 
  • Brain stem: The brain stem connects the brain with the spinal cord. It controls breathing, body temperature, blood pressure, and other basic body functions.
brain parts
This picture shows the major parts of the brain
Tumor Grades and Types

When most normal cells grow old or get damaged, they die, and new cells take their place. Sometimes, this process goes wrong. New cells form when the body doesn’t need them, and old or damaged cells don’t die as they should. The buildup of extra cells often forms a mass of tissue called a growth or tumor.

Primary 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. 
    • Benign brain tumors usually have an obvious border or edge. Cells from benign tumors rarely invade tissues around them. They don’t 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.
    • Benign brain tumors may become malignant. 
  • Malignant brain tumors (also called brain cancer) contain cancer cells: 
    • Malignant brain tumors are generally more serious and often are a threat to life. 
    • They are likely to grow rapidly and crowd or invade the nearby healthy brain tissue.
    • Cancer cells may break away from malignant brain tumors and spread to other parts of the brain or to the spinal cord. They rarely spread to other parts of the body.
Tumor Grade

Doctors group brain tumors by grade. The grade of a tumor refers to the way the cells look under a microscope:
  • Grade I: The tissue is benign. The cells look nearly like normal brain cells, and they grow slowly. 
  • Grade II: The tissue is malignant. The cells look less like normal cells than do the cells in a Grade I tumor. 
  • Grade III: The malignant tissue has cells that look very different from normal cells. The abnormal cells are actively growing (anaplastic). 
  • Grade IV: The malignant tissue has cells that look most abnormal and tend to grow quickly. 
Cells from low-grade tumors (grades I and II) look more normal and generally grow more slowly than cells from high-grade tumors (grades III and IV).

Over time, a low-grade tumor may become a highgrade tumor. However, the change to a high-grade tumor happens more often among adults than children.

You may want to read the NCI fact sheet Tumor Grade.

Types of Primary Brain Tumors

There are many types of primary brain tumors. Primary brain tumors are named according to the type of cells or the part of the brain in which they begin. For example, most primary brain tumors begin in glial cells. This type of tumor is called a glioma.

Among adults, the most common types are:
  • Astrocytoma: The tumor arises from star-shaped glial cells called astrocytes. It can be any grade. In adults, an astrocytoma most often arises in the cerebrum.
    • Grade I or II astrocytoma: It may be called a low-grade glioma
    • Grade III astrocytoma: It’s sometimes called a high-grade or an anaplastic astrocytoma. 
    • Grade IV astrocytoma: It may be called a glioblastoma or malignant astrocytic glioma. 
  • Meningioma: The tumor arises in the meninges. It can be grade I, II, or III. It’s usually benign (grade I) and grows slowly. 
  • Oligodendroglioma: The tumor arises from cells that make the fatty substance that covers and protects nerves. It usually occurs in the cerebrum. It’s most common in middle-aged adults. It can be grade II or III. 
Among children, the most common types are:
  • Medulloblastoma: The tumor usually arises in the cerebellum. It’s sometimes called a primitive neuroectodermal tumor. It is grade IV. 
  • Grade I or II astrocytoma: In children, this lowgrade tumor occurs anywhere in the brain. The most common astrocytoma among children is juvenile pilocytic astrocytoma. It’s grade I. 
  • Ependymoma: The tumor arises from cells that line the ventricles or the central canal of the spinal cord. It’s most commonly found in children and young adults. It can be grade I, II, or III. 
  • Brain stem glioma: The tumor occurs in the lowest part of the brain. It can be a low-grade or high-grade tumor. The most common type is diffuse intrinsic pontine glioma. You can find more information about types of brain tumors at http://www.cancer.gov/cancertopics/ types/brain. Or, you can call the NCI Contact Center at 1–800–4–CANCER (1–800–422–6237).
Risk Factors  

When you’re told that you have a brain tumor, it’s natural to wonder what may have caused your disease. But no one knows the exact causes of brain tumors. Doctors seldom know why one person develops a brain tumor and another doesn’t. 

Researchers are studying whether people with certain risk factors are more likely than others to develop a brain tumor. A risk factor is something that may increase the chance of getting a disease. 

Studies have found the following risk factors for brain tumors: 
  • Ionizing radiation: Ionizing radiation from highdose x-rays (such as radiation therapy from a large machine aimed at the head) and other sources can cause cell damage that leads to a tumor. People exposed to ionizing radiation may have an increased risk of a brain tumor, such as meningioma or glioma. 
  • Family history: It is rare for brain tumors to run in a family. Only a very small number of families have several members with brain tumors. 
Researchers are studying whether using cell phones, having had a head injury, or having been exposed to certain chemicals at work or to magnetic fields are important risk factors. Studies have not shown consistent links between these possible risk factors and brain tumors, but additional research is needed.
by: Meyda Azzahra
source: Unram