Brain Tumor Glossary of Terms

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

Observational Study

A type of study in which individuals are observed or certain outcomes are measured. No attempt is made to affect the outcome (for example, no treatment is given).

Occipital brain tumor

A tumor in the area of or relating to the occipital lobe. The occipital lobe is the posterior lobe of each cerebral hemisphere that is separated medially from the parietal lobe by the parieto-occipital sulcus, is indistinctly separated more laterally from the temporal and parietal lobes, bears the visual areas, and has the form of a 3-sided pyramid.


Describes the legal use of a prescription drug to treat a disease or condition for which the drug has not been approved by the U.S. Food and Drug Administration.


Also called a mixed glioma, an astrocytoma with a high proportion of oligodendroglioma cells.


A cell that forms the myelin sheath (a layer that covers and protects nerve cells) in the brain and spinal cord. An oligodendrocyte is a type of glial cell.

Oligodendroglial Tumor

A rare, slow-growing tumor that begins in oligodendrocytes (cells that cover and protect nerve cells in the brain and spinal cord). Also called oligodendroglioma.


Oligodendroglioma. May be subdivided into primary brain tumors and the more common, secondary brain tumors. Primary brain tumors (for example astrocytoma, craniopharyngioma, glioma, ependymoma, neuroglioma, oligodendroglioma, glioblastoma multiforme, meningioma, medulloblastoma) arise from the uncontrolled proliferation of cells within the brain. Secondary brain tumors occur from the spread of cancer into the brain from a distant cancerous organ (metastasis).


Gene that is a mutated (changed) form of a gene involved in normal cell growth. Oncogenes may cause the growth of cancer cells. Mutations in genes that become oncogenes can be inherited or caused by being exposed to substances in the environment that cause cancer.


A doctor who specializes in treating cancer. Some oncologists specialize in a particular type of cancer treatment. For example, a radiation oncologist specializes in treating cancer with radiation.


The study of cancer.


The lysis (breakdown) of cancer cells. This can be caused by chemical or physical means (for example, strong detergents or high-energy sound waves) or by infection with a strain of virus that can lyse cells.

Open Label Study

A type of study in which both the health providers and the patients are aware of the drug or treatment being given.

Optic glioma

A slow-growing glioma of the optic nerve or optic chiasm heralded by visual loss, often with secondary strabismus followed by proptosis and loss of ocular movements.

Overall Survival Rate

The percentage of people in a study or treatment group who are alive for a certain period of time after they were diagnosed with or treated for a disease, such as cancer. The overall survival rate is often stated as a five-year survival rate, which is the percentage of people in a study or treatment group who are alive five years after diagnosis or treatment. Also called survival rate.