View source for Oligodendroglioma

'''For patient information click [[{{PAGENAME}} (patient information)|here]]'''.

{{Infobox_Disease |
  Name           = {{PAGENAME}} |
  Image          = |
  Caption        = |
  DiseasesDB     = 29450 |
  ICD10          = C71 |
  ICD9           = {{ICD9|191.9}} |
  ICDO           = 9450/3-9451/3 |
  OMIM           = |
  MedlinePlus    = |
  MeshID         = D009837 |
}}
{{Oligodendroglioma}}
{{CMG}}

{{EH}}

==[[Oligodendroglioma overview|Overview]]==

==[[Oligodendroglioma historical perspective|Historical Perspective]]==

==[[Oligodendroglioma pathophysiology|Pathophysiology]]==

==[[Oligodendroglioma epidemiology and demographics|Epidemiology & Demographics]]==

==[[Oligodendroglioma risk factors|Risk Factors]]==

==[[Oligodendroglioma screening|Screening]]==

==[[Oligodendroglioma causes|Causes]]==

==[[Oligodendroglioma differential diagnosis|Differentiating Oligodendroglioma]]==

==[[Oligodendroglioma natural history|Complications & Prognosis]]==

==Diagnosis==
[[Oligodendroglioma history and symptoms|History and Symptoms]] | [[Oligodendroglioma physical examination|Physical Examination]] | [[Oligodendroglioma staging|Staging]] | [[Oligodendroglioma laboratory tests|Laboratory tests]] | [[Oligodendroglioma electrocardiogram|Electrocardiogram]]  | [[Oligodendroglioma x ray|X Rays]] | [[Oligodendroglioma CT|CT]] | [[Oligodendroglioma MRI|MRI]] [[Oligodendroglioma echocardiography or ultrasound|Echocardiography or Ultrasound]] | [[Oligodendroglioma other imaging findings|Other images]] | [[Oligodendroglioma other diagnostic studies|Alternative diagnostics]]

==Treatment==
[[Oligodendroglioma medical therapy|Medical therapy]] | [[Oligodendroglioma surgery|Surgical options]] | [[Oligodendroglioma primary prevention|Primary prevention]]  | [[Oligodendroglioma secondary prevention|Secondary prevention]] | [[Oligodendroglioma cost-effectiveness of therapy|Financial costs]] | [[Oligodendroglioma future or investigational therapies|Future therapies]]

==Etiology==
The etiology of oligodendrogliomas is unknown. Some studies have linked oligodendroglioma with a viral cause, a single case report has linked oligodendroglioma to irradiation of pituitary adenoma.

==Symptoms==
In anywhere from fifty to eighty percent of cases, the first symptom of an oligodendroglioma is the onset of [[seizure]] activity. They occur mainly in the [[frontal lobe]] thus affecting personality.
[[Headaches]] combined with increased [[intracranial pressure]] are also a common symptom of oligodendroglioma. Depending on the location of the tumor, any neurological deficit can be induced, from visual loss, motor weakness and cognitive decline. A [[Computed Tomography]] (CT) or [[Magnetic Resonance Imaging]] (MRI) scan is necessary to characterize the anatomy of this tumor (size, location, heter/homogeneity). However, final diagnosis of this [[tumor]], like most tumors, relies on [[histopathologic]] examination ([[biopsy]] examination).

==Microscopic Appearance==
Oligodendrogliomas cannot currently be differentiated from other brain lesions solely by their clinical or radiographic appearance.  As such, a brain [[biopsy]] is the only method of definitive diagnosis.  Oligodendrogliomas recapitulate the appearance of the normal resident [[oligodendroglia]] of the brain.  (Their name derives from the Greek roots 'oligo' meaning “ few” and 'dendro' meaning “trees”.)  They are generally composed of cells with small to slightly enlarged round nuclei with dark, compact nuclei and a small amount of eosinophilic cytoplasm.  They are often referred to as "fried egg" cells due to their histologic appearance. They appear as a monotonous population of mildly enlarged round cells infiltrating normal brain parenchyma and producing vague nodules.  Although the tumor may appear to be vaguely circumscribed, it is by definition a diffusely infiltrating tumor.    

Classically they tend to have a vasculature of finely branching capillaries that may take on a “chicken wire” appearance .  When invading grey matter structures such as cortex, the neoplastic oligodendrocytes tend to cluster around [[neurons]] exhibiting a phenomenon referred to as “perineuronal satellitosis”.  Oligodendrogliomas may invade preferentially around vessels or under the [[pia mater|pial]] surface of the brain.  

Oligodendrogliomas must be differentiated from the more common [[astrocytoma]].  Non-classical variants and combined tumors of both oligodendroglioma and astrocytoma differentiation are seen, making this distinction controversial between different [[neuropathology]] groups.  In the US, in general, neuropathologists trained on the West Coast are more liberal in the diagnosis of oligodendroliomas than either East Coast or Midwest trained neuropathologists who render the diagnosis of oligodendroglioma for only classic variants.  Molecular diagnostics may make this differentiation obsolete in the future.  

Other [[glioma|glial]] and glioneuronal tumors with which they are often confused due to their monotonous round cell appearance include [[pilocytic astrocytoma]], central neurocytoma, the so-called [[dysembryoplastic neuroepithelial tumor]], or occasionally [[ependymoma]].

==Histopathological Grading==

The histopathologic grading of oligodendrogliomas is controversial.  Currently the most commonly used grading schema is based on year 2007 [[World Health Organization]] (WHO) guidelines.  Oligodendrogliomas are generally dichotomized into grade II (low grade) and grade III (high grade) tumors.  The designation of grade III oligodendroglioma (high grade) generally subsumes the previous diagnoses of anaplastic or malignant oligodendroglioma.  

Unfortunately, the WHO guidelines include subjective criteria in differentiating grade II and grade III tumors including the appreciation of “significant” hypercellularity and pleomorphism in the higher grade lesion.  In addition, the presence of low mitotic activity, vascular proliferation and necrosis, including pseudopallisading necrosis are insufficient by themselves to elevate the grade of these tumors.  This leads to inevitable interobserver variability in diagnosis by pathologists.  The ultimate responsibility for making treatment decisions and interpretation of these diagnoses lies with the oncologist in consultation with the patient and their family.     

It has been proposed that [[World Health Organization|WHO]] guidelines should contain a category for grade IV oligodendrogliomas which essentially appear to be glial neoplasms with overwhelming features of [[glioblastoma multiforme]] (GBM) arising from known lower grade oligodendrogliomas or GBM with a significant proportion of oligodendroglial differentiation.   The diagnostic ultility of this latter category is uncertain as these tumors may behave either like glioblastoma or grade III oligodendrogliomas.  As such, this is an exceptionally unusual diagnosis.  

The updated WHO guidelines published in 2007 recommends classifying such tumors for the time being as ‘glioblastoma with oligodendroglioma component’. <ref>{{cite journal |author=Louis D, Ohgaki H, Wiestler O, 'et al'' |title=The 2007 WHO Classification of Tumours of the Central Nervous System |journal=Acta Neuropathologica |volume=114 |issue=2 |pages=97-109 |year=2007 |pmid=17618441 |doi=10.1007/s00401-007-0243-4}}</ref> It remains to be established whether or not these tumors carry a better prognosis than standard glioblastomas. 

==Molecular genetics==
By far, the most common structural deformity found is co-deletion of chromosomal arms 1p and 19q. The high frequency of co-deletion (60-80%) is a striking feature of this glial tumour, and is considered as a "genetic signature" of oligodendroglioma. 1p/19q deletion has been correlated with both chemosensitivity and improved prognosis in oligodendrogliomas.<ref>{{cite journal |author=Laigle-Donadey F, Benouaich-Amiel A, Hoang-Xuan K, Sanson M |title=[Molecular biology of oligodendroglial tumors] |language=French |journal=Neuro-Chirurgie |volume=51 |issue=3-4 Pt 2 |pages=260-8 |year=2005 |pmid=16292170 |doi=}}</ref><ref>{{cite journal |author=Walker C, Haylock B, Husband D, ''et al'' |title=Clinical use of genotype to predict chemosensitivity in oligodendroglial tumors |journal=Neurology |volume=66 |issue=11 |pages=1661-7 |year=2006 |pmid=16769937 |doi=10.1212/01.wnl.0000218270.12495.9a}}</ref>
A t(1;19)(q10;p10) translocation mediates the combined deletions of 1p and 19q. The gene products lost as a consequence of this codeletion may include mediators of resistance to genotoxic therapies. Alternatively, 1p/19q loss might be an early oncogenic lesion promoting the formation of glial neoplasms, which retain high sensitivity to genotoxic stress.

==Prognosis & treatment==
Oligodendrogliomas are generally felt to be incurable using current treatments.  However compared to the more common [[astrocytomas]], they are slowly growing with prolonged survival.  In one series, [[median]] survival times for oligodendrogliomas were 11.6 years for grade II and 3.5 years for grade III.<ref> Ohgaki H, Kleihues P. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=15977639&query_hl=10&itool=pubmed_docsum Population-based studies on incidence, survival rates, and genetic alterations in astrocytic and oligodendroglial gliomas.] ''J Neuropathol Exp Neurol''. 2005 Jun;64(6):479-89. PMID: 15977639</ref>  Because of the indolent nature of these tumors and the potential [[morbidity]] associated with [[neurosurgery]], [[chemotherapy]] and [[radiation therapy]], most [[oncology|neurooncologists]] will initially pursue a course of [[watchful waiting]] and treat patients symptomatically.  Symptomatic treatment often includes the use of [[anticonvulsants]] for seizures and [[Glucocorticoid|steroids]] for [[oedema|brain swelling]].  PCV chemotherapy ([[Procarbazine]], [[Lomustine|CCNU]] and [[Vincristine]]) has been shown to be effective and is currently the most commonly used chemotherapy regimen used for treating anaplastic oligodendrogliomas.<ref>Herbert H. Engelhard, M.D., Ph.D., Ana Stelea, M.D., and Arno Mundt, M.D.[http://www.virtualtrials.com/pdf/oligo.pdf] p.452</ref> [[Temozolomide]] is a common chemotheraputic drug to which oligodendrogliomas appear to be quite sensitive.  It is often used as a first line therapy.  

Because of their diffusely infiltrating nature, oligodendrogliomas cannot be completely resected and are not curable by [[surgery|surgical excision]].  If the tumor mass compresses adjacent brain structures, a [[neurosurgery|neurosurgeon]] will typically remove as much of the tumor as he or she can without damaging other critical, healthy brain structures. Surgery may be followed up by [[chemotherapy]], [[radiation]], or a mix of both. Oligodendrogliomas, like all other infiltrating [[gliomas]], have a very high (almost uniform) rate of recurrence and gradually increase in grade over time.  Recurrent tumors are generally treated with more aggressive chemotherapy and radiation therapy. Recently, [[stereotactic surgery]] has proven successful in treating small tumors that have been diagnosed early. 

Long-term survival is reported in a minority of patients.<ref>Tatter SB. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=12392640&query_hl=7&itool=pubmed_DocSum Recurrent malignant glioma in adults.] ''Curr Treat Options Oncol''. 2002 Dec;'''3'''(6):509-24. PMID: 12392640,</ref> With aggressive treatment and close monitoring, it is possible to outlive the typical life expectancies for both low grade and high grade oligodendrogliomas. In rare cases, patients have survived for up to fifteen years post-diagnosis. Westergaard’s
study (1997) showed that patients younger than 20 years had a median survival of 17.5 years.<ref>Herbert H. Engelhard, M.D., Ph.D., Ana Stelea, M.D., and Arno Mundt, M.D.[http://www.virtualtrials.com/pdf/oligo.pdf] p.449</ref> Another study shows a 34% survival rate after 20 years. <ref> {{cite journal |author=Feigenberg SJ, Amdur RJ, Morris CG, Mendenhall WM, Marcus RB, Friedman WA |title=Oligodendroglioma: does deferring treatment compromise outcome? |journal=Am. J. Clin. Oncol. |volume=26 |issue=3 |pages=e60-6 |year=2003 |pmid=12796617 |doi=10.1097/01.COC.0000072507.25834.D6}}</ref>

==References==
{{Reflist|2}}

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