Background
Oligodendrogliomas (ODs) are primary glial brain tumors that are divided into grade II and anaplastic grade III tumors (World Health Organization [WHO] criteria). Typically, they have an indolent course, and patients may survive for many years after symptom onset. Their good prognosis relative to other parenchymal tumors probably stems from inherently less aggressive biological behavior and a favorable response to chemotherapy, a recently discovered finding based on genetic characteristics.
Pathophysiology
Oligodendrogliomas arise in the cerebral hemispheres and are distributed among the frontal, parietal, temporal, and occipital lobe, in approximately a 3:2:2:1 ratio. Rarely, they can arise in the cerebellum, brain stem, and spinal cord. [1] They usually occur in the cerebral white matter and are very cellular, with uniform nuclei. They react with glial fibrillary acidic protein on immunostaining.
Epidemiology
Frequency
United States
The incidence of oligodendrogliomas ranges from 5-19% of all intracranial tumors. The newer studies showed incidence of oligodendrogliomas to be around 25% of all gliomas. This may be explained by the improvements in the treatment of oligodendrogliomas, prompting neuropathologists to favor the diagnosis.
International
No difference in the incidence of oligodendroglioma exists worldwide.
Mortality/Morbidity
The morbidity and mortality profile for oligodendrogliomas is much better than for astrocytic tumors. However, it also depends on tumor location and pressure effects, as with any other intracranial lesion. The median survival from initial diagnosis of all low-grade oligodendrogliomas (LGOs) is 4-10 years, but it is only 3-4 years for anaplastic oligodendrogliomas.
Race
No difference exists among the races.
Sex
Oligodendrogliomas occur in both sexes, with a male-to-female predominance of 2:1.
Age
Oligodendrogliomas may be diagnosed at any age but occur most commonly in young and middle-aged adults, with a median age at diagnosis of 40-50 years. In children, only 6% of gliomas are diagnosed as oligodendrogliomas.
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Classic histologic image of oligodendroglioma. This image shows monomorphous tumoral proliferation that consists of round, regular cells with a small, central, hyperchromatic nucleus surrounded by clear cytoplasm. Few calcifications are present.
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Smear preparation of anaplastic oligodendroglioma. This image reveals increased nuclear pleomorphism and vascular proliferation.
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Contrast-enhanced computed tomography scan in a 44-year-old man with a 3-year history of epileptic seizures. This image reveals a calcified hypoattenuating lesion that is invading the corpus callosum.
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Computed tomography scan of a low-grade oligodendroglioma. This image reveals a well-demarcated, left frontal hypoattenuating lesion with a small calcification.
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Sagittal gadolinium-enhanced T1-weighted magnetic resonance image of a low-grade oligodendroglioma. This image demonstrates no contrast enhancement.
