A WHO grade III oligodendroglial tumor is a fast-growing brain tumor that starts from oligodendrocytes, the cells that make the myelin (insulation) around nerve fibers. In today’s World Health Organization (WHO) system, this tumor is officially called “oligodendroglioma, IDH-mutant and 1p/19q-codeleted, CNS WHO grade 3.” That name describes two key genetic features that must be present to make the diagnosis: a mutation in the IDH gene and the combined loss (codeletion) of parts of chromosomes 1p and 19q. These tumors are part of the “adult-type diffuse gliomas” family and are graded as grade 2 or grade 3; grade 3 tumors grow and spread more quickly within the brain than grade 2 tumors. Cancer.gov+3PMC+3PMC+3
A WHO grade III oligodendroglial tumor is a malignant (faster-growing) brain tumor that starts in the cells that support nerve cells (oligodendrocytes). In the current WHO system, its exact name is “oligodendroglioma, IDH-mutant and 1p/19q-codeleted, CNS WHO grade 3.” This means the tumor carries a change (mutation) in an enzyme called IDH and has lost parts of chromosomes 1p and 19q. Doctors diagnose grade 3 when the cells look more aggressive under the microscope or when certain genes (like CDKN2A/B homozygous deletion) are present, which indicates worse behavior. PMC+2Nature+2
You may still see “anaplastic oligodendroglioma,” but WHO 2021 removed the “anaplastic” label and integrated molecular features (IDH and 1p/19q) into the official name. The older mitotic-count cutoffs are no longer used as hard rules because evidence didn’t show a clean boundary. J Pathol Transl Med+1
Other names
You may still see older or alternative names in reports, websites, or older studies. Common ones include:
Anaplastic oligodendroglioma – this was the older name used for grade III tumors. The 2021 WHO update recommends using “grade 3” instead of “anaplastic,” but many clinicians and papers still use the older term. College of American Pathologists
Oligodendroglioma, IDH-mutant and 1p/19q-codeleted (grade 3) – the current WHO name. PMC
Oligodendroglial tumor – a broader, less specific label sometimes used in older pathology reports. Modern practice avoids vague labels and requires the IDH mutation and 1p/19q codeletion to confirm the diagnosis. Nature
Types
Strictly speaking, WHO recognizes one entity—oligodendroglioma, IDH-mutant and 1p/19q-codeleted—and assigns a grade 2 (slower-growing) or grade 3 (faster-growing). There is no grade 4 oligodendroglioma in the current system. Grade 3 is based on more aggressive microscopic features such as higher mitotic activity; some molecular findings can also “signal” worse behavior. For example, homozygous deletion of CDKN2A/B is being used by many centers as a marker of grade 3 biology. Clinically, grade 3 tumors may either arise de novo as grade 3 or progress from a prior grade 2 oligodendroglioma over time. Nature+1
Causes
Most oligodendrogliomas are sporadic, meaning we do not know the exact cause. However, doctors understand important molecular events and risk patterns. Each item below is brief to keep it clear.
IDH1/IDH2 mutation: This is a key early change that helps drive the tumor. It is required (together with 1p/19q codeletion) for diagnosis in adults. PMC
1p/19q codeletion: Loss of the short arm of chromosome 1 and the long arm of chromosome 19 is a hallmark; it shapes how the tumor behaves and responds to therapy. ARUP Consult
t(1;19) whole-arm translocation: A chromosomal swap that explains how the 1p/19q codeletion happens in many tumors. PMC
TERT promoter mutation: Common in oligodendroglioma and linked with the classic molecular profile. PMC+1
MGMT promoter methylation (epigenetic change): Not a cause by itself, but often present and may predict better response to alkylating chemotherapy. Cancer.gov
Progression from a prior grade 2 oligodendroglioma: Some grade 3 tumors evolve from lower-grade disease. PMC
Ionizing radiation (prior exposure): Radiation is a recognized risk factor for primary brain tumors in general, though it explains only a small fraction of cases. (General CNS tumor risk, not specific to oligodendroglioma.) Cancer.gov
Inherited cancer syndromes (rare): Conditions like Li-Fraumeni or Lynch syndrome can raise glioma risk, but oligodendroglioma is still uncommon even in these groups. Cancer.gov
Family history of glioma (rare): Slightly higher risk has been reported for close relatives, but most cases have no family history. Cancer.gov
Adult age: These tumors are mainly adult-type diffuse gliomas. PMC
Frontal lobe predilection: Not a cause, but a common location pattern that shapes symptoms. Radiological Society of North America
Male sex (slight excess in some series): Epidemiology reports often show a small male predominance. Radiological Society of North America
De-novo grade 3 biology: Some tumors appear at first diagnosis with grade 3 features; the molecular profile supports their faster growth. Nature
Tumor microenvironment changes: Abnormal blood vessels and supporting cells may support tumor growth; these are effects that help the tumor, not primary causes. PMC
Copy-number changes beyond 1p/19q: Additional chromosome changes can accumulate and drive progression. PMC
CDKN2A/B homozygous deletion: A change linked to worse outcomes and used by many to flag grade 3 behavior. Wiley Online Library
DNA repair pathway alterations: Interactions with MGMT and other repair genes can influence treatment response and progression risk. Cancer.gov
Metabolic rewiring from IDH mutation: The IDH mutation produces 2-HG, which changes cell programs and contributes to tumor formation. PMC
Prior chemotherapy/radiation of a lower-grade oligodendroglioma: Over long periods, some treated grade 2 tumors still progress biologically to grade 3. Cancer.gov
Unknown environmental factors: Studies of lifestyle or chemical exposures are inconclusive; no consistent everyday exposure has been proven to cause oligodendroglioma. (Consensus across guidelines and reviews.) Cancer.gov
Symptoms
Symptoms depend on tumor location and size. Many patients have long-standing symptoms because these tumors can grow slowly before speeding up.
Seizures (very common): Many people with oligodendroglioma first seek care due to a seizure. ScienceDirect+1
Headache: From pressure or irritation in the brain. Cancer.gov
Personality or behavior change: Frontal lobe tumors may cause apathy, irritability, or poor judgment. Cancer.gov
Memory and thinking problems: Trouble focusing or slower thinking may appear. Cancer.gov
Weakness on one side (arm/leg): From involvement of motor pathways. Cancer.gov
Numbness or tingling: Sensory pathways can be affected. Cancer.gov
Speech or language problems: Word-finding issues or slurred speech when language areas are involved. Cancer.gov
Vision problems: Blurred or double vision, or visual field cuts, depending on the area. Cancer.gov
Nausea/vomiting: Often related to increased pressure in the skull. Cancer.gov
Balance or coordination trouble: If pathways for movement are affected. Cancer.gov
Fatigue: Common in brain tumors and after seizures. Cancer.gov
Confusion or episodes of “spacing out”: Sometimes short staring spells are seizure equivalents. PMC
Aphasia (difficulty understanding or producing language): When the dominant hemisphere language centers are involved. Cancer.gov
Visual seizures (flashing lights) or focal sensory spells: Depending on location. PMC
Symptoms that slowly worsen over months or years: Fits the typical natural history before grade 3 behavior emerges. Cancer.gov
Diagnostic tests
A) Physical examination (bedside neurologic exam)
General neurologic exam: The doctor checks alertness, orientation, cranial nerves, muscle strength, reflexes, sensation, coordination, and walking. Findings may point to the brain area affected and guide urgent imaging. Cancer.gov
Fundoscopy (looking at the back of the eye): Swelling of the optic disc (papilledema) can suggest raised intracranial pressure from a mass. This prompts urgent imaging. Cancer.gov
Cognitive screening (e.g., MoCA/MMSE): Quick bedside tests of memory, attention, and language help document baseline function and track change over time. They do not diagnose the tumor but capture its effects. Cancer.gov
B) Manual/bedside functional tests
Bedside visual field testing: Simple confrontation testing can pick up field cuts from tumors near visual pathways. It guides imaging and referrals. Cancer.gov
Language tasks (naming, repetition, fluency): Short tasks can reveal aphasia when the tumor involves language cortex. Results help plan advanced testing and surgery mapping. Cancer.gov
Motor strength and fine motor tasks (rapid alternating movements, finger tapping): These quick manual tests help detect subtle weakness or slowness caused by tumor involvement. Cancer.gov
Gait and balance testing (tandem gait, Romberg): Simple maneuvers can uncover coordination issues and guide rehab referral. Cancer.gov
C) Laboratory and pathological tests (the definitive diagnosis)
Stereotactic biopsy or surgical resection with histology: Tissue is essential. A neuropathologist examines the tumor under the microscope to confirm a diffuse glioma and assess grade-3 features (e.g., increased mitoses). Nature
IDH1 (R132H) immunohistochemistry and IDH sequencing: Tests for the IDH mutation required for diagnosis. If staining is negative, DNA sequencing checks for non-R132H variants. Nature
1p/19q codeletion testing (FISH/NGS): Detects the hallmark combined loss of 1p and 19q. Both IDH mutation and 1p/19q codeletion must be present for oligodendroglioma. ARUP Consult
ATRX and p53 immunohistochemistry: In oligodendroglioma, ATRX is typically retained and p53 is usually low, helping separate it from IDH-mutant astrocytoma (which often shows ATRX loss and p53 over-expression). BTRT
TERT promoter testing: Frequently mutated in oligodendroglioma; part of the typical molecular profile. PMC
CDKN2A/B status (copy-number testing): Homozygous deletion is associated with more aggressive behavior and may be used to support grade-3 biology. Wiley Online Library
MGMT promoter methylation: Helps predict sensitivity to alkylating chemotherapy (e.g., temozolomide/PCV). Not diagnostic by itself. Cancer.gov
D) Electrodiagnostic tests
Electroencephalography (EEG) for seizure evaluation: EEG is the standard test to document and classify seizures, which are common with oligodendroglioma. It helps localize the seizure focus and guide treatment. Medscape+1
Continuous or peri-operative EEG monitoring (when indicated): Sometimes used after surgery or around high-risk periods to catch non-obvious seizures and guide anti-seizure therapy. SpringerLink
Evoked potentials / intraoperative mapping (specialized centers): During surgery near language or motor areas, mapping and neurophysiologic monitoring help remove tumor safely while preserving function. (Supportive techniques; not diagnostic alone.) Cancer.gov
E) Imaging tests
MRI brain with and without contrast: The main imaging test. Oligodendrogliomas often appear T2/FLAIR bright, may enhance variably, and commonly show calcifications (seen best on CT). Advanced MRI (perfusion, spectroscopy, diffusion) helps with grading and planning. PMC+1
CT head: Useful to detect calcifications and for quick evaluation in emergencies. Calcification is frequent in oligodendroglioma. Medscape
Functional or metabolic imaging when available: Techniques like MR perfusion, MR spectroscopy, and amino-acid PET (e.g., FET-PET) can help estimate tumor grade, choose biopsy targets, and assess progression vs. treatment effect. PMC
Non-pharmacological treatments (therapies & other supports)
Each entry gives: description (~150 words), purpose, and mechanism/rationale.
Maximal safe surgical resection
Description. A neurosurgeon aims to remove as much tumor as safely possible without harming critical brain functions. Techniques may include image guidance, awake language mapping, and 5-ALA fluorescence (where appropriate). Removing more tumor usually improves control of the disease. Purpose. Reduce tumor load, relieve pressure, and extend the time before regrowth; enable more accurate diagnosis and adjuvant planning. Mechanism. Physical debulking lowers the number of cancer cells and may improve the effectiveness of radiation/chemotherapy that follows. PMCPrecision radiotherapy
Description. After healing from surgery, patients typically receive focused external-beam radiotherapy. Purpose. Kill remaining tumor cells, improve local control, and prolong survival. Mechanism. Ionizing radiation damages DNA in cancer cells. Modern planning shapes dose tightly to the target while sparing healthy tissue. ScienceDirectNeuro-oncology rehabilitation (physio/OT/speech)
Description. Tailored physical therapy, occupational therapy, and speech-language therapy address weakness, balance, fatigue, speech or swallowing difficulty, and daily-living skills. Purpose. Preserve independence and safety, reduce disability, and support return to routine. Mechanism. Task-specific training and neuroplasticity principles help the brain adapt and re-route functions after surgery or radiation. PMCCognitive rehabilitation
Description. Structured memory, attention, and executive-function training with therapists and digital tools. Purpose. Improve everyday thinking, work ability, and quality of life. Mechanism. Repeated practice, strategy training, and compensatory techniques tap brain plasticity and improve coping with cognitive side effects. PMCSeizure safety education
Description. Counseling on triggers, sleep hygiene, medication adherence, driving/work restrictions, and first-aid for seizures. Purpose. Reduce injury risk and anxiety; support self-management. Mechanism. Knowledge plus routines decrease missed doses and risky exposures; coordinated care reduces emergency visits. NatureSteroid-sparing edema strategies
Description. Use the lowest effective dexamethasone dose for the shortest time; taper as symptoms allow; add gastric protection, glucose monitoring, and exercise to limit steroid side effects. Purpose. Control brain swelling while minimizing complications (infection, muscle weakness, high blood sugar). Mechanism. Dexamethasone reduces blood-brain barrier leakiness; careful dosing/tapering lowers harm. Alberta Health Services+1Amino-acid PET or advanced MRI guidance (where available)
Description. Centers may use amino-acid PET (e.g., FET-PET) or perfusion/spectroscopy MRI to refine tumor boundaries and detect recurrence vs treatment effect. Purpose. Improve accuracy of treatment planning and follow-up decisions. Mechanism. Tumors take up tracers or show blood-flow/metabolic changes that look different from injured but non-cancerous tissue. The LancetExercise & fatigue management
Description. Progressive, supervised aerobic and resistance exercise adjusted to symptoms. Purpose. Lessen fatigue, improve mood, cardiorespiratory fitness, and day-to-day function during and after treatment. Mechanism. Exercise modulates inflammation, improves mitochondrial function, and supports neurotrophins—benefits shown across many cancers. PubMedPalliative and supportive care (early integration)
Description. Specialist input for symptom relief (pain, fatigue, mood, sleep), advance-care planning, and caregiver support—from diagnosis, not only near end-of-life. Purpose. Better quality of life, less distress, and more goal-concordant care. Mechanism. Multidisciplinary symptom control and psychosocial support reduce suffering and improve decision-making. BTRTPsychological counseling & peer support
Description. Individual or group counseling, mindfulness-based stress reduction, and caregiver resources. Purpose. Reduce anxiety/depression and improve coping. Mechanism. Evidence-based psychotherapies and social support improve resilience and treatment adherence. PMC
(If you’d like, I can expand this section to a full list of 20 therapies with the same detail.)
Drug treatments
For each, I include a plain description (~150 words where helpful), drug class, typical dosing framework, timing, purpose, mechanism, and key side effects. Exact prescriptions must be individualized by the oncology team.
1) PCV regimen (Procarbazine + Lomustine/CCNU + Vincristine)
Class. Alkylating agent (lomustine), cytotoxic/MAOI-like (procarbazine), microtubule-inhibitor (vincristine).
Dose/Timing (typical EORTC 26951 reference pattern). Lomustine 110 mg/m² on day 1; Procarbazine 60 mg/m² daily days 8–21; Vincristine 1.4 mg/m² (cap 2 mg) IV on days 8 & 29; cycles every 6 weeks × up to 6, adjusted for counts/toxicity. Start after RT.
Purpose. Proven survival benefit when added to RT in 1p/19q-codeleted tumors.
Mechanism. Multidrug DNA-damage and mitotic arrest.
Side effects. Myelosuppression, neuropathy (vincristine), nausea, fatigue; procarbazine has MAOI-like food/drug interactions and a disulfiram-like alcohol reaction—patients must follow low-tyramine guidance and avoid alcohol. Cancer Care Ontario+4PubMed+4NCCN+4
2) Temozolomide (TMZ)
Class. Oral alkylating agent.
Dose/Timing. Commonly 75 mg/m² daily during RT (~42 days), then after 4 weeks 150–200 mg/m² daily on days 1–5 every 28 days for 6+ cycles, adjusted by counts/toxicity.
Purpose. Widely used alternative to PCV (easier to give); definitive survival comparison vs PCV awaits CODEL.
Mechanism. DNA methylation (O6-guanine) leading to tumor cell death.
Side effects. Lymphopenia, thrombocytopenia, nausea, fatigue; PJP prophylaxis may be considered with prolonged concurrent dosing. eviQ+2FDA Access Data+2
3) Dexamethasone (edema relief, symptom control)
Class. Corticosteroid.
Dose/Timing. Use the lowest effective dose (e.g., 4–8 mg/day for mild symptoms; higher for severe, then taper).
Purpose. Quickly reduces brain swelling and improves headaches, focal deficits, and nausea.
Mechanism. Stabilizes blood-brain barrier and lowers vasogenic edema.
Side effects. High blood sugar, infection risk, muscle weakness, mood changes; taper to minimize harm. Alberta Health Services
4) Levetiracetam (seizure control)
Class. Antiepileptic.
Dose/Timing. Often begins 500 mg twice daily, titrating up (usual max 1500 mg twice daily). Do not give prophylactically to patients without seizures, per neuro-oncology practice updates.
Purpose. Treats tumor-related seizures with few drug interactions.
Mechanism. Modulates synaptic vesicle protein SV2A to reduce abnormal neuronal firing.
Side effects. Somnolence, irritability; adjust for kidney function. Drugs.com+1
5) Antiemetics (e.g., ondansetron) during chemo
Class. 5-HT3 antagonists.
Dose/Timing. Per chemotherapy days/schedules.
Purpose. Prevent nausea/vomiting from alkylating agents.
Mechanism. Blocks serotonin receptors in the gut/brain.
Side effects. Constipation, headache; rare QT prolongation. HSE.ie
6) PJP prophylaxis during prolonged concurrent chemoradiation (case-by-case)
Class. Antimicrobials (e.g., TMP-SMX).
Dose/Timing. When immunosuppression risk is high (e.g., extended daily TMZ + RT).
Purpose. Reduce Pneumocystis infection risk.
Mechanism. Antifolate/antimicrobial activity.
Side effects. Rash, cytopenias; consider alternatives in allergy. Cancer Care Ontario
7) Proton-pump inhibitor or H2 blocker during high-dose steroids
Class. Acid suppression.
Dose/Timing. While on moderate–high dose dexamethasone.
Purpose. Reduce steroid-related GI irritation/ulcer risk.
Mechanism. Lowers gastric acid.
Side effects. With prolonged use: infection risk, low magnesium (PPIs). eviQ
8) IDH-targeted therapy (investigational/selected use)
Class. IDH1/2 inhibitors (e.g., vorasidenib; ivosidenib).
Dose/Timing. Vorasidenib is approved for residual or recurrent low-grade IDH-mutant diffuse glioma; its role in grade 3 is not established outside trials.
Purpose. Target the mutant IDH enzyme to slow tumor metabolism.
Mechanism. Inhibits 2-HG production to normalize epigenetics and growth signals.
Side effects. Elevated liver enzymes, fatigue; monitor per label/trial. Physio Update+1
(I can continue and expand to a full list of 20 drugs if you want each with the same detail; in practice, most grade 3 oligodendroglioma pathways revolve around PCV/TMZ, steroids as needed, antiseizure meds if seizures, and supportive medicines.)
Dietary molecular supplements
Important: No vitamin, herb, or over-the-counter supplement has been proven to control oligodendroglioma. Some can be harmful or interact with treatment—especially with procarbazine (MAOI-like) where tyramine-rich foods and alcohol should be avoided. Always clear supplements with your oncology team. Mayo Clinic+1
Vitamin D — Often checked and replaced if low for general health; no tumor-control proof. Avoid mega-doses. PMC
Omega-3 (fish oil) — May help triglycerides/inflammation; stop before surgery if advised (bleeding risk uncertain); no anti-glioma proof. PMC
Probiotics — Can ease antibiotic-related gut symptoms; avoid if severely immunosuppressed. No tumor effect. PMC
Melatonin — May help sleep; limited neuro-oncology data. Discuss drug interactions. PMC
Magnesium — Replace only if deficient; high doses can cause diarrhea. PMC
B-complex (no high B6) — Correct deficiency only; very high B6 can cause neuropathy. PMC
Protein supplements — Useful for appetite loss; choose low-tyramine options if on procarbazine. Drugs.com
Green-tea extract / curcumin — Laboratory interest only; clinical benefit unproven and possible drug interactions. PMC
Ketogenic diet products — Evidence in glioma is limited/early; not standard of care. American Academy of Neurology
Electrolyte solutions — Helpful during chemo-related nausea; check sugar content if on steroids. PMC
Immunity-booster / regenerative / stem-cell” drugs
Honest status. There are no approved “immunity booster” or stem-cell drugs that cure or control oligodendroglioma. Several experimental approaches (oncolytic viruses, vaccines, CAR-T) are studied mainly in glioblastoma and, when appropriate, inside clinical trials. Dosing is protocol-specific and not recommended outside trials. Oxford Academic+1
Oncolytic adenovirus (DNX-2401) — Virus injected into tumor to lyse cells and spark immunity; early trials in high-grade glioma show some long survivors; still investigational. ASCO Publications+1
IDH1 R132H peptide vaccines — Immune vaccine aimed at the common IDH1 mutation; early-phase signals, not standard. U.S. Food and Drug Administration
CAR-T cells — Reprogrammed T-cells targeting glioma antigens; small studies show activity in GBM; durability remains a challenge; trials ongoing. Reuters+1
Tumor Treating Fields (TTFields) — Non-drug, device therapy approved for glioblastoma; not established for oligodendroglioma. Lippincott Journals
Mesenchymal stem-cell carriers — Early trials explore stem-cell-based delivery systems; not approved. ClinicalTrials.gov
Combinatorial oncolytic viro-immunotherapy — Research stage; clinical use limited to trials. MDPI
Surgeries
Initial craniotomy with awake mapping (as needed). Removes tumor while testing speech/motor in real time to protect function. Why: Maximize safe resection, which helps control disease and symptoms. PMC
Re-resection at recurrence (select cases). If tumor regrows in an operable area and recovery is likely. Why: Debulk, relieve symptoms, obtain fresh tissue for updated molecular testing or trials. PMC
Stereotactic biopsy. Needle sampling when a safe large resection isn’t possible. Why: Secure diagnosis and molecular markers to guide therapy. PMC
CSF diversion (ventricular drain/shunt). For tumor-related hydrocephalus. Why: Relieve dangerous pressure from blocked fluid pathways. PMC
Laser interstitial thermal therapy (LITT) (select centers). MRI-guided laser ablation for small, deep recurrences. Why: Minimally invasive debulking when open surgery is high-risk. PMC
Prevention tips
There is no known way to prevent this tumor. These tips help reduce treatment risks and keep you safer during care:
Keep every MRI and clinic visit (usually every 3–6 months initially). Missing follow-up can delay detection of regrowth. NCCN
Take medicines exactly as prescribed; bring a list to visits. PMC
If on procarbazine (PCV), avoid alcohol and high-tyramine foods to prevent severe reactions. Cancer Care Ontario
Watch for steroid side effects (thirst, infection, weakness) and report promptly; taper as advised. Alberta Health Services
Practice seizure safety (sleep, adherence, supervision for risky tasks). Nature
Stay active (gentle exercise most days) to reduce fatigue and deconditioning during therapy. PubMed
Vaccinations (e.g., influenza) per oncology advice; avoid live vaccines if immunosuppressed. PMC
Nutrition counseling early if appetite/weight change. PMC
Palliative-care consult early for symptom control and planning. BTRT
Ask about trials at major centers, especially at recurrence. NCCN
When to see a doctor urgently
Worsening headache, severe morning nausea/vomiting, or any new neurological symptom (weakness, speech trouble, vision change).
New or more frequent seizures.
Fever, cough, or infections while on steroids or chemotherapy.
Severe reaction after eating/drinking while on procarbazine (pounding headache, flushing, palpitations)—this may be a tyramine or alcohol interaction.
These are red-flags your team wants to know about immediately.
Disclaimer: Each person’s journey is unique, treatment plan, life style, food habit, hormonal condition, immune system, chronic disease condition, geological location, weather and previous medical history is also unique. So always seek the best advice from a qualified medical professional or health care provider before trying any treatments to ensure to find out the best plan for you. This guide is for general information and educational purposes only. Regular check-ups and awareness can help to manage and prevent complications associated with these diseases conditions. If you or someone are suffering from this disease condition bookmark this website or share with someone who might find it useful! Boost your knowledge and stay ahead in your health journey. We always try to ensure that the content is regularly updated to reflect the latest medical research and treatment options. Thank you for giving your valuable time to read the article.
The article is written by Team RxHarun and reviewed by the Rx Editorial Board Members
Last Updated: September 16, 2025.
