Sign Up for a Free Account
  • Updated 04.19.2024
  • Released 02.15.1996
  • Expires For CME 04.19.2027




Oligodendrogliomas are diffusely infiltrating chemoresponsive gliomas defined by the presence of mutated isocitrate dehydrogenase 1 (IDH1) or IDH2 and whole-arm chromosomal losses of 1p and 19q. The integration of genetic parameters IDH, ATRX, and 1p/19q has resulted in far fewer misdiagnoses, and in turn, it has improved correlations with prognosis and treatment response for diffuse gliomas as a group. The authors review the evolving approach to the diagnosis and management of this tumor.

Key points

• Oligodendrogliomas are diffusely infiltrating chemoresponsive gliomas defined by the presence of mutated IDH1 or IDH2 and whole-arm chromosomal losses of 1p and 19q. Their growth trajectory is typically slower compared to astrocytomas IDH mutated and glioblastoma IDH wild-type, though no less fatal in advanced stages of disease.

• The goal of treatment is to prolong survival and delay further progression, and a multidisciplinary approach with surgery, radiation, and chemotherapy is often warranted.

• The optimal timing of postsurgical treatment is variable and may be guided by assessing the risk of early progression against the risk of treatment-related adverse effects.

Historical note and terminology

In 1926, Bailey and Cushing conceived a classification system for glial tumors and are credited with coining the term oligodendroglioma. Their system relied on histopathological features and emphasized morphological similarities with different neuronal cell types, such as oligodendrocytes and astrocytes, at different developmental stages. Tumors exhibiting histologic characteristics of both astrocytoma and oligodendroglioma were referred to as mixed glioma or oligoastrocytoma. A grading system for gliomas initially proposed by Kernohan in 1938 and modified by others acknowledged a possible correlation between the degree of tumor anaplasia and biological behavior. In 1979, the World Health Organization published its initial consensus classification and grading system for central nervous system neoplasms. It was internationally well-received, and periodic updates maintain its relevancy.

Before the 2016 update of the World Health Organization classification system, oligodendroglial tumors were subdivided into two groups: grade 2 (low-grade) and grade 3 (anaplastic). Although the favorable prognosis of oligodendroglioma over astrocytoma had long been recognized, the clinical significance could not be defined by histology alone. There was little reason to distinguish oligodendroglioma from astrocytoma, let alone oligoastrocytoma, particularly in the context of clinical trials. This changed following initial reports of the chemosensitive nature of oligodendroglioma, resulting in increased attention to such tumors (11).

The discovery of molecular and genetic alterations, such as simultaneous whole-arm deletions of chromosomes 1p and 19q (1p/19q codeletion) and mutations in isocitrate dehydrogenase (IDH), offered further insight into the biology and behavior of diffuse gliomas. Both features are associated with improved prognosis. The prognostic and predictive significance was striking enough to warrant revision of the existing World Health Organization classification for brain tumors to integrate molecular analysis into the overall diagnosis. Oligodendroglioma is now defined by the presence of IDH mutation and whole-arm 1p/19q loss; the presence of an IDH mutation in the absence of 1p/19q codeletion results in a diagnosis of astrocytoma. As a consequence, the term oligoastrocytoma is considered irrelevant, in which case the designation “not otherwise specified” (NOS) is used. Reports of gliomas exhibiting genetic evidence of both oligodendroglioma (1p/19q codeletion) and astrocytoma (TP53 and ATRX mutations) are rare and likely represent two morphologically and molecularly distinct subclones within a single IDH-mutant diffuse glioma.

This is an article preview.
Start a Free Account
to access the full version.

  • Nearly 3,000 illustrations, including video clips of neurologic disorders.

  • Every article is reviewed by our esteemed Editorial Board for accuracy and currency.

  • Full spectrum of neurology in 1,200 comprehensive articles.

  • Listen to MedLink on the go with Audio versions of each article.

Questions or Comment?

MedLink®, LLC

3525 Del Mar Heights Rd, Ste 304
San Diego, CA 92130-2122

Toll Free (U.S. + Canada): 800-452-2400

US Number: +1-619-640-4660



ISSN: 2831-9125