Oligodendroglioma is a WHO grade 2 or 3 diffusely infiltrative glial tumor originating from oligodendroglial cells. Per WHO 2021 classification, both IDH mutation and 1p/19q codeletion are required for diagnosis. It constitutes approximately 5-20% of all gliomas. It typically occurs in adults aged 30-50, with cortical and subcortical location, especially in the frontal lobe. The most distinctive imaging feature is coarse calcification. It has better prognosis compared to astrocytomas and responds better to chemotherapy (PCV).
Age Range
30-60
Peak Age
45
Gender
Male predominant
Prevalence
Uncommon
Oligodendroglioma is a diffusely infiltrative tumor arising from oligodendrocyte precursor cells. Diagnostically, co-occurrence of IDH1/2 mutation and 1p/19q chromosomal codeletion is mandatory — this molecular signature defines oligodendroglial differentiation. The 1p/19q codeletion results from t(1;19)(q10;p10) translocation and is the strongest predictor of response to PCV chemotherapy. The tumor prominently infiltrates cortical gray matter and extends into subcortical white matter — seizure is the most common presenting symptom due to this cortical location. Calcification is the most characteristic pathological feature of oligodendroglioma (in 70-90% of cases); calcification formation is related to disrupted calcium metabolism in tumor cells. The tumor grows by infiltrating individually within brain parenchyma but shows slow proliferation and variable blood-brain barrier integrity.
A cortical-subcortical mass in the frontal lobe containing coarse calcification is the most diagnostic imaging finding of oligodendroglioma. Calcification is present in 70-90% of oligodendrogliomas and is best evaluated on CT. This pattern strongly supports the diagnosis of oligodendroglioma in a young-to-middle-aged adult with seizure history.
On non-contrast CT, the most characteristic finding of oligodendroglioma is observed: coarse calcification within a cortical-subcortical mass. Calcification is present in 70-90% of cases and may show scattered, coarse, nodular, or gyriform (following gyri) patterns. Hypodense tumoral component is observed around the calcification. Cortical expansion is prominent — the tumor infiltrates and thickens the cortex, expanding it outward. Mass effect is generally minimal relative to size. Cystic components may be of variable size and number. Hemorrhagic foci may be present.
Report Sentence
A hypodense mass measuring approximately _x_x_ cm is identified in the right/left frontal lobe with cortical-subcortical location, containing foci of coarse calcification, with cortical expansion.
On T1-weighted sequences, a heterogeneous hypointense cortical-subcortical mass is observed. Hypointensity reflects increased water content from tumoral infiltration. Calcification areas show variable signal on T1 — generally hypointense but some calcification types may appear hyperintense due to T1 shortening. Cystic components are T1 hypointense, hemorrhagic components are T1 hyperintense. Enhancement on T1 post-contrast is variable — usually minimal or patchy in grade 2, more prominent and heterogeneous in grade 3.
Report Sentence
On T1-weighted sequences, a heterogeneous hypointense mass with cortical-subcortical location is observed, with variable/patchy enhancement on post-contrast T1 sequences.
On T2-weighted sequences, a heterogeneous hyperintense cortical-subcortical mass is observed. Heterogeneity results from the combination of calcification (T2 hypointense signal voids), cystic areas (markedly T2 hyperintense), hemorrhage (variable T2), and solid tumor tissue (T2 hyperintense). This heterogeneous T2 pattern is an important distinguishing feature of oligodendroglioma — astrocytoma generally appears homogeneous T2 hyperintense. Cortical infiltration appears as cortical thickening and signal increase on T2. Tumor margins are ill-defined (infiltrative growth).
Report Sentence
On T2-weighted sequences, a heterogeneous hyperintense mass with cortical-subcortical location is observed, with hypointense signal void areas due to calcification, cystic components, and cortical expansion.
FLAIR sequences best demonstrate cortical infiltration of oligodendroglioma. CSF signal suppression allows better evaluation of tumoral infiltration at the cortical surface compared to T2. Cortical thickening, signal increase, and blurring of gray-white matter differentiation (cortical blurring) are observed. FLAIR is also superior to T2 for evaluating tumor margins. Calcification appears hypointense on FLAIR as well. Peritumoral edema is variable and usually minimal relative to size.
Report Sentence
On FLAIR sequences, cortical thickening and signal increase consistent with cortical infiltration are observed in the frontal lobe, with blurring of gray-white matter differentiation.
In grade 2 oligodendroglioma, diffusion restriction is generally not significant — ADC values are normal or mildly elevated. In grade 3 (anaplastic) oligodendroglioma, diffusion restriction may be more prominent due to increased cellularity. ADC values are inversely proportional to tumor grade. Calcification areas may complicate evaluation on DWI due to susceptibility artifacts. Minimum ADC value indicates the most aggressive tumor region and is used for biopsy guidance.
Report Sentence
On DWI, no significant diffusion restriction is observed in the mass, with ADC values within normal limits. Susceptibility artifact is present in calcification areas.
On perfusion MRI, rCBV in grade 2 oligodendroglioma is generally low-to-moderate (1.0-2.0). Importantly, some grade 2 oligodendrogliomas may show elevated rCBV — this reflects the 'chicken-wire vascularity' histological feature and should not be misinterpreted as higher grade. Leakage correction is especially important in oligodendroglioma because contrast leakage may underestimate rCBV. In grade 3 oligodendroglioma, rCBV is generally higher (>2.0).
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On perfusion MRI, low-to-moderate rCBV values are observed in the mass (rCBV: ___). Leakage-corrected analysis has been applied.
On MR spectroscopy, 2-HG peak at 2.25 ppm is positive for IDH-mutant oligodendroglioma — non-invasive indicator of IDH mutation. Choline is mildly to moderately elevated (may be higher compared to astrocytoma). NAA is reduced. Glutamate-glutamine (Glx) complex may be elevated. Myoinositol elevation is characteristic of low-grade gliomas. Lipid-lactate peak is generally absent in grade 2, may appear in grade 3. Voxel should be placed avoiding calcification areas — calcification degrades MRS quality.
Report Sentence
MR spectroscopy demonstrates 2-HG peak at 2.25 ppm, mildly elevated choline, reduced NAA, and elevated myoinositol in the lesion, consistent with IDH-mutant glial neoplasm.
Criteria
IDH1/2 mutation and 1p/19q codeletion positive, low mitotic activity, no necrosis or microvascular proliferation. WHO 2021 diagnostic triad.
Distinct Features
Prominent calcification, cortical location, minimal enhancement, low rCBV, good prognosis (median survival >10 years), good response to PCV chemotherapy.
Criteria
IDH mutation and 1p/19q codeletion positive, increased mitotic activity and/or microvascular proliferation or necrosis. Oligodendroglioma showing anaplastic features.
Distinct Features
More prominent enhancement, elevated rCBV (>2.0), lower ADC values, more prominent heterogeneous appearance. Still good treatment response due to 1p/19q codeletion and better prognosis than astrocytic grade 3 (median survival 7-10 years).
Criteria
Previously defined as a mixed glioma containing both oligodendroglial and astrocytic components in older WHO classifications. Removed in WHO 2021 — advances in molecular profiling allow all mixed gliomas to be classified as either oligodendroglioma (1p/19q+) or astrocytoma (ATRX loss).
Distinct Features
No longer a valid diagnosis. Previously diagnosed 'oligoastrocytoma' tumors are reclassified as either IDH-mutant oligodendroglioma or IDH-mutant astrocytoma through molecular reclassification.
Distinguishing Feature
Low-grade astrocytoma: calcification rare, homogeneous T2 signal, no enhancement, ATRX loss, 1p/19q negative. Oligodendroglioma: calcification common (70-90%), heterogeneous T2 signal, variable enhancement, ATRX retained, 1p/19q positive.
Distinguishing Feature
Meningioma: extra-axial, CSF cleft, dural tail, intense homogeneous enhancement, psammomatous calcification. Oligodendroglioma: intra-axial, cortical infiltration, no CSF cleft, variable enhancement, coarse intratumoral calcification.
Distinguishing Feature
GBM: ring enhancement, central necrosis, elevated rCBV, low ADC, calcification rare, usually >50 years, IDH-wildtype. Oligodendroglioma: variable enhancement, calcification common, low-to-moderate rCBV, usually 30-50 years, IDH-mutant + 1p/19q.
Distinguishing Feature
Central neurocytoma: intraventricular mass at lateral ventricle near septum pellucidum/foramen of Monro, calcification, bubbly appearance, young adult. Oligodendroglioma: intraparenchymal cortical-subcortical mass, not intraventricular.
Urgency
routineManagement
Cerrahi: maksimal güvenli rezeksiyon. Yüksek risk (>40 yaş, subtotal rezeksiyon, derece 3): erken adjuvan RT + PCV kemoterapisi (1p/19q ko-delesyonu PCV yanıtının en güçlü öngörücüsü). Düşük risk (genç, gross total rezeksiyon, derece 2): aktif izleme veya erken adjuvan tedavi.Biopsy
NeededFollow-up
İlk yıl her 3-6 ayda, ardından yıllık kontrastlı MRG. Yeni kontrast tutulumu, rCBV artışı, ADC düşüşü veya kalsifikasyon artışı malign transformasyon şüphesi ile rebiyopsi gerektirir. Oligodendrogliomlar tedaviye iyi yanıt verir ve uzun sağkalım beklenir (derece 2: >10 yıl, derece 3: 7-10 yıl).Oligodendroglioma is the subtype with the best prognosis among diffuse gliomas. The 1p/19q codeletion is the strongest molecular predictor of sensitivity to PCV chemotherapy and radiotherapy. Molecular profiling (IDH, 1p/19q, ATRX) is mandatory for diagnosis — histological appearance alone is insufficient. Advanced MRI techniques (perfusion, MRS) are valuable for grading and transformation monitoring. Calcification presence is a diagnostic clue on CT but may be missed on MRI — CT calcification investigation is recommended in suspected glioma cases.
Oligodendrogliomas have the best prognosis among diffuse gliomas. 1p/19q co-deletion indicates sensitivity to chemotherapy (PCV) and radiotherapy. Median survival is 12-15 years for Grade 2 and 7-10 years for Grade 3. Seizures are the most common presentation (50-80%). Treatment is surgery plus adjuvant chemoradiation.