A patient's guide to brain tumor and brain pathology terms.

1p/19q codeletion

Genetic alteration encountered in oligodendroglial tumors. The presence of this alteration in the right context is associated with a better prognosis in diffuse gliomas of adults, and usually results in a different treatment.


A subtype of glioma that has features in common with astrocytes; an astrocyte is a subtype of glial cell that has a variety of functions in the brain, including reacting and filling space after an area of injury and regulating the blood brain barrier.

Central Nervous System (CNS)

A complex organ system that includes the brain and spinal cord.

Cerebrospinal Fluid (CSF)

Fluid that surrounds the brain and spinal cord and fills the ventricles. Some malignant brain tumor types have a propensity to spread through this fluid, and cells of these tumors may be identified through microscopic analysis.

Embryonal Tumors

Group of malignant tumors that are most common in children and young patients. They share features in common with the developing Central Nervous System.


Subgroup of tumors that have are most common in the brain in children and the spinal cord in adults. They form well circumscribed masses and the primary treatment involves surgical resection, although chemotherapy and irradiation may be required for higher grade tumors.


A disorder of the brain characterized by recurrent convulsions (seizures).

Fluorescence in situ hybridization (FISH)

Molecular technique that applies “probes” for specific gene regions and is useful in identifying gains (amplifications) and gene losses (e.g. 1p/19q) in tumors.


Generic term for supporting cells in the Central Nervous System other than neurons. It includes astrocytes, oligodendrocytes and microglia.


Most common primary malignant brain neoplasm characterized by its aggressive behavior and infiltrative behavior in the brain.


Broad category of brain tumors that includes astrocytomas and oligodendrogliomas.


Scale used to assess the potential aggressiveness of brain tumors. Brain tumors may be broadly classified as low grade or high grade.

High Grade

Applied to tumors with a high proliferative rate and malignant features.


Isocitrate dehydrogenase 1. Metabolic enzyme. Mutations in this gene are a feature of a diffuse glioma subset associated with a better prognosis.


Special staining technique that recognizes the levels of specific molecules, such as proteins, characteristic of particular tumor types.


The partial or complete suppression of the immune response of an individual; immunosuppression is induced to help the survival of an organ after a transplant operation.

Low Grade

Applied to tumors usually with a slower growth potential.


Most common primary malignant brain tumor in children. Highly aggressive but many patients are curable with current treatments.


Tissues that cover and surround the brain and contain the cerebrospinal fluid.


Common brain tumor that develops in association with meninges and may compress the brain or spinal cord from the outside.


Tumors that start outside of the brain in other organs (e.g. lung, breast) but that reach the brain through the circulation.

MGMT Methylation

Molecular genetic characteristic of specific subgroups of brain tumors—particularly glioblastoma—and associated with a higher sensitivity for specific chemotherapies (such as temozolomide).

Microvascular Proliferation

Increased number and abnormal configuration of small vessels in brain tumors. A marker of higher grade in diffuse gliomas.


Alterations in the DNA of specific genes. May characterize specific brain tumor types. Mutations may be somatic (present in the tumor tissue only) or germline (present in multiple or all cells of the patient as well as the tumor).


Areas of dead cells or tissues. Necrosis is a marker of higher grade in diffuse gliomas.


Physicians specializing in the medical treatment of brain tumors.

Next Generation Sequencing

Laboratory technique that allows for the testing of alterations of multiple genes simultaneously. Increasingly applied to tumor diagnosis and treatment.


Glioma subtype characterized by particular morphologic features (uniform round cells) and molecular genetic alterations (1p/19q codeletion, IDH mutation) and associated with relatively better outcome among the diffuse gliomas affecting adults.

Polymerase Chain Reaction (PCR)

Common laboratory technique used to test alterations in specific genes.


Cavities located inside the brain containing the cerebrospinal fluid.

WHO Classification

Standard guide for the classification and grading of human cancer, including brain tumors. Guidelines are established by brain tumor experts from around the world every few years.