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Tumors that originate in the brain (compared to those that spread to the brain from elsewhere in the body) are called primary tumors, which 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.

Tumor Types

Among adults, there are several brain tumors that start in the glial cells:

Astrocytoma — This tumor arises from star-shaped glial cells called astrocytes. It can be any grade (see information below about 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 is sometimes called a high-grade or an anaplastic astrocytoma.
  • Grade IV astrocytoma: It may be called a glioblastoma or malignant astrocytic glioma.

Ependymoma — This tumor starts in the epedymal cells and makes up 2 to 3 percent of all intracrianial tumors.

Glioblastoma Multiforme — This type of glial tumor is the most invasive. It typically grows and spreads quickly, and has a poor prognosis. It may be made up of different cells, including astrocytes and oligodendrocytes.

Oligodendroglioma — This tumor arises from cells that make the fatty substance that covers and protects nerves. It usually occurs in the cerebrum. It is most common in middle-aged adults. It can be grade II or III.

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 high-grade tumor. However, the change to a high-grade tumor happens more often among adults than children.

In general, what are brain tumors?

Brain tumors are abnormal growths of tissue found inside the skull, which is a primary component of the central nervous system (CNS). Benign tumors are noncancerous and malignant tumors are cancerous. The CNS is housed within rigid, bony quarters (i.e., the skull), so any abnormal growth, whether benign or malignant, can place pressure on sensitive tissues and impair function.

Tumors that originate in the brain are called primary tumors. Most primary tumors are caused by out-of-control growth among cells that surround and support neurons. In a small number of individuals, primary tumors may result from specific genetic disease (e.g., neurofibromatosis, tuberous sclerosis) or from exposure to radiation or cancer-causing chemicals.

The cause of most primary tumors remains a mystery. They are not contagious and, at this time, not preventable. Symptoms of brain tumors include headaches, seizures, nausea and vomiting, vision or hearing problems, behavioral and cognitive problems, motor problems and balance problems.

The first test to diagnose brain tumors is a neurological examination. Special imaging techniques (such as computed tomography, magnetic resonance imaging and positron emission tomography) are also employed. Laboratory tests include the EEG and the spinal tap. A biopsy, a surgical procedure in which a sample of tissue is taken from a suspected tumor, helps doctors diagnose the type of tumor.

Is there any treatment?

The three most commonly used treatments are surgery, radiation, and chemotherapy. Doctors also may prescribe steroids to reduce the swelling inside the CNS.

What is the prognosis?

Symptoms of brain tumors generally develop slowly and worsen over time unless they are treated. The tumor may be classified as benign or malignant and given a numbered score that reflects how malignant it is. This score can help doctors determine how to treat the tumor and predict the likely outcome, or prognosis, for the patient.

What research is being done?

Researchers are studying brachytherapy (small radioactive pellets implanted directly into the tumor) and advanced drugs and techniques for chemotherapy and radiation therapy. In gene therapy for brain tumors, scientists insert a gene to make the tumor cells sensitive to certain drugs, to program the cells to self-destruct, or to instruct the cells to manufacture substances to slow their growth.

Scientists are also investigating why some genes become cancer-causing. Since tumors are more sensitive to heat than normal tissue, research scientists are testing hyperthermia as a treatment by placing special heat-producing antennae into the tumor region after surgery. In immunotherapy, scientists are looking for ways to duplicate or enhance the body's immune response to fight against brain and spinal cord cancer.

Primary Brain Tumors: Benign or Malignant

When most normal cells grow old or get damaged they die, with new cells taking 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 build-up 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