oligodendroglioma
Meaning of oligodendroglioma: A brain tumor from the cells that insulate nerve fibers, now identified by a pair of genetic changes rather than by appearance alone.
Definition of oligodendroglioma
Oligodendroglioma is a brain tumor that arises from oligodendrocytes, the cells that wrap nerve fibers in a fatty insulating sheath. It grows slowly, usually in the frontal or temporal lobe, and often announces itself with a first seizure in an adult. Its diagnosis now rests on two specific genetic findings as well as the appearance of the cells under a microscope.
What do oligodendrocytes normally do?
A nerve fiber carries an electrical signal, and bare fiber carries it slowly. Oligodendrocytes solve that by wrapping each fiber in myelin, a fatty sheath laid down in segments with small gaps between them. The signal jumps from gap to gap instead of creeping along the whole length, which speeds it up many times over. One oligodendrocyte reaches out and wraps segments of several different fibers at once.
How is it diagnosed?
Under the microscope the cells look uniform and round, with a clear halo around each nucleus that pathologists describe as a fried egg appearance, set against a delicate branching pattern of small vessels. That look alone is no longer enough. The diagnosis now requires two molecular findings: a mutation in an enzyme called IDH, and the loss of one copy each of two chromosome arms, known as 1p/19q codeletion. A brain tumor that looks the part but lacks those changes is classified as something else.
How does it differ from other gliomas?
| Tumor | Cell of origin | Typical pace |
|---|---|---|
| Oligodendroglioma | Myelin-forming cells | Slow, often over years |
| Astrocytoma | Star-shaped support cells | Slow to moderate |
| Glioblastoma | Glial cells, poorly differentiated | Fast |
Why does the genetic signature matter?
The 1p/19q codeletion is not only a label. Tumors carrying it respond better to chemotherapy and radiation than gliomas that do not, and people with them tend to live considerably longer. That is why the test is performed on every specimen with this appearance, and why two tumors that look alike down a microscope can be given different names and different outlooks.
Also known as
Used in a sentence
Histology and molecular testing together confirmed an oligodendroglioma of the left frontal lobe.
Good to know
The appearance under the microscope is no longer sufficient for the diagnosis, which requires an IDH mutation together with loss of chromosome arms 1p and 19q.
Word origin
Where “oligodendroglioma” comes from
Built from the Greek oligos, meaning few, dendron, meaning tree, and glia, meaning glue, with the suffix -oma denoting a swelling or tumor.