Brain Tumor Glossary of Terms

Easily explore the meaning of hundreds of medical terms or words, many directly used in brain tumor-related terminology.

Magnetic Resonance Angiogram (MRA)

MRA:The magnetic resonance angiogram, or MRA, is a noninvasive test that has demonstrated usefulness in defining the anatomy of blood vessels of certain size in the head and neck. MRA serves as a complement to traditional MRI scanning in evaluation of the brain and neck. Conventional angiograms, whereby contrast material is injected through a catheter into the blood vessels of the head and neck, are the gold standard (most accurate) for determining the anatomy of these vessels. The advantages of MRA is that it is faster and easier (it does not involve the catheters, contrast material, and risks of angiograms). Another advantage is that MRA also gives an image of the tissue of the brain. MRA is a general term that refers to various imaging techniques that are used to visualize the blood vessels by using magnetic resonance (MR) signal changes that are affected by changes in the flow of blood caused by changes in the shape of the blood vessels. MRA can be used to detect small ballooning of the blood vessels (aneurysms) as small as 4 millimeters in diameter. Smaller aneurysms can require an angiogram for detection. The sensitivity of MRA in detecting aneurysms can be affected by bleeding within the brain and the location of the aneurysms within the brain. MRA can also detect abnormal design (malformations), and atherosclerosis of blood vessels within the brain. Atherosclerosis of the carotid arteries of the neck can be visualized with MRA. MRA does not have significant application for the detection or definition of cancer of the brain.

Magnetic Resonance Imaging Scan (MRI)

The MRI, which uses magnetic fields, not X-rays, to provide detailed images, is more sensitive than the CT in detecting a brain tumor's presence. The MRI is a preferential imaging test because it outlines the normal brain structure in unique detail. The test procedure is slightly more time consuming as the patient lies inside a cylinder-type machine for about one hour. A special dye may also be injected in the bloodstream during the procedure (MRI angiogram) to distinguish tumors from healthy tissue.

Magnetic Resonance Perfusion Imaging

A special type of magnetic resonance imaging (MRI) that uses an injected dye in order to see blood flow through tissues. Also called perfusion magnetic resonance imaging.

Magnetic Resonance Spectroscopy (MRS)

A noninvasive imaging method that provides information about cellular activity (metabolic information). It is used along with magnetic resonance imaging (MRI) which provides information about the shape and size of the tumor (spatial information). Also called 1H-nuclear magnetic resonance spectroscopic imaging, MRSI, and proton magnetic resonance spectroscopic imaging.


A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Malignant cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of malignancy. Carcinoma is a malignancy that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a malignancy that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a malignancy that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are malignancies that begin in the cells of the immune system. Central nervous system cancers are malignancies that begin in the tissues of the brain and spinal cord. Also called cancer.


Cancerous. Malignant tumors can invade and destroy nearby tissue and spread to other parts of the body.

Malignant Brain Tumor

Malignant brain tumors do not have distinct borders and tend to grow rapidly, causing pressure within the brain. It is highly unlikely for malignant brain tumors to spread beyond the central nervous system.

* Malignant tumors are more serious and often life-threatening
* Cells can break from the malignant brain tumor, spreading to other parts of the brain or to the spinal cord. Rarely do these cancerous cells spread to other parts of the body


In medicine, a lump in the body. It may be caused by the abnormal growth of cells, a cyst, hormonal changes, or an immune reaction. A mass may be benign (not cancer) or malignant (cancer).

Medulla oblongata

The most vital part of the entire brain, continuing as the bulbous portion of the spinal cord just above the foramen magnum and separated from the pons by a horizontal groove. It is one of three parts of the brainstem . The medulla contains the cardiac (heart),vasomotor and the respiratory centers of the brain.


The medulloblastoma is highly malignant (grade IV) and usually originates in the cerebellum, the region of the brain that plays an important role in the integration of sensory perception, coordination and motor control. Also:

* Type of primitive neuroectodermal tumor, which is invasive and rapidly growing
* Unlike most brain tumors, spreads through the cerebrospinal fluid and frequently metastasizes to other locations in the brain and spine
* Most occur near brain stem
* May obstruct fourth ventricle, causing water on the brain
* Occurs most often in children under age 10, but can occur in adults
* Slightly more common in males than females

Medulloblastomas account for 25 percent of pediatric brain tumors. The annual U.S. incidence rate: two per 100,000.


Having to do with the meninges (three thin layers of tissue that cover and protect the brain and spinal cord).


The three thin layers of tissue that cover and protect the brain and spinal cord.


The tumor grows from the meninges, the layers of tissue covering the brain and spinal cord. As it grows, meningioma compresses other brain tissue which can affect cranial nerves. Sometimes the growth extends into facial bones, producing visible changes.

It is usually benign (grade I) or low-grade. Still, the meningioma tumor can cause disability and be life-threatening. It also can be grade II or III. Also:

* Cannot predict its rate of growth or how long it was growing prior to diagnosis
* Can arise after previous treatment from ionizing radiation or excessive X-ray exposure
* Grows slowly, which sometimes allows the brain to become accustomed to its presence
* Occurs at any age, but common among men and women, 40s to 50s
* Twice as common in women
* Can invade skull or metastasize to skin or lungs, although rare

Meningiomas represent about 25-30 percent of all primary brain tumors. The annual U.S. incidence rate is: two per 100,000.


Inflammation of the meninges (three thin layers of tissue that cover and protect the brain and spinal cord). Meningitis is usually caused by a bacterial or viral infection, but sometimes is caused by cancer, drug allergies, or inflammatory diseases.


Surgery to remove one or more metastases (tumors formed from cells that have spread from the primary tumor). When all metastases are removed, it is called a complete metastasectomy.


The spread of cancer from one part of the body to another. A tumor formed by cells that have spread is called a “metastatic tumor” or a “metastasis.” The metastatic tumor contains cells that are like those in the original (primary) tumor. The plural form of metastasis is metastases.


To spread from one part of the body to another. When cancer cells metastasize and form secondary tumors, the cells in the metastatic tumor are like those in the original (primary) tumor.


Having to do with metastasis, which is the spread of cancer from the primary site (place where it started) to other places in the body.

Metastatic Brain Tumor

A brain tumor caused by cancer elsewhere in the body spreading to the brain.

Metastatic Cancer

Cancer that has spread from the place in which it started to other parts of the body.


In medicine, the rules and procedures for doing research and evaluating results.


Small numbers of cancer cells that have spread from the primary tumor to other parts of the body and are too few to be picked up in a screening or diagnostic test.


The process by which a single parent cell divides to make two new daughter cells. Each daughter cell receives a complete set of chromosomes from the parent cell. This process allows the body to grow and replace cells.

Mitotic Activity

Having to do with the presence of dividing (proliferating) cells. Cancer tissue generally has more mitotic activity than normal tissues.

Mixed Glioma

A brain tumor that forms from more than one type of brain cell, usually astrocytes and oligodendrocytes.


A disease or the incidence of disease within a population. Morbidity also refers to adverse effects caused by a treatment.

Multicenter Study

A clinical trial that is carried out at more than one medical institution.


Any change in the DNA of a cell. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Mutations can be harmful, beneficial, or have no effect. If they occur in cells that make eggs or sperm, they can be inherited; if mutations occur in other types of cells, they are not inherited. Certain mutations may lead to cancer or other diseases.


A medical procedure for examining the spinal cord by means of X rays. It is especially useful in diagnosing spinal abscesses and tumors and dislocated intervertebral disks.