Oligodendroglioma (WHO grade II) is a well-differentiated tumor, composed predominantly of cells morphologically resembling oligodendroglia, which grows diffusely in the cortex and white matter. 
This tumor is uncommon and accounts for approximately 50% of oligodendroglial tumors and between 5 and 18% of all gliomas. Most oligodendrogliomas occur in adults, with a peak incidence in the 5 and 6 decades of life, with the subcortical area as the most common location. 
Compared to patients with astrocytoma, patients with oligodendroglioma respond better to radiation therapy and chemotherapy.
Temozolomide appears to have activity in low-grade oligodendrogliomas and oligoastrocytomas combined with a 1p allelic loss. Clinical improvement was noted in 51% of patients, and the radiologic response rate was 31%. 
Anaplastic (malignant) oligodendrogliomas
Anaplastic or malignant oligodendrogliomas may occur with an increased cellularity, cell pleomorphisms and fast growth rates, and a bad prognosis. In a clinical environment, one only differentiates between low grade and anaplastic oligodendroglioma. 
Imaging studies of oligodendrogliomas are useful for the differential diagnosis based on location, lesion characteristics, presence of calcification, and mass effect. The typical imaging finding of oligodendroglioma is the calcification identified on unenhanced CT. The calcification is present in more than 85% of tumors. In MRI, oligoastrocytomas appear iso- to hypointense on T1 with very low intensity, representing the calcified areas. On T2 or FLAIR, the tumors are typically hyperintense.
Fig.1 General view of Olygodendroglioma
Fig.2 Morphology of Olygodendroglioma
- M.F. Reiser, W. Semmler, H. Hricak (Eds.) "Magnetic Resonance Tomography", Springer 2008