Oligodendroglioma 

General:
- Adult tumor
- poorly circumscribed, parenchymal, infiltrating growth pattern
- WHO grade II (standard)
- WHO grade III (anaplastic) - more mitotically active
- If there is necrosis, it is considered a GBM
- Better prognosis than infiltrating astrocytomas - may be because they respond better to therapy

- Can occur anywhere in the brain - including intraventricularly (may resemble central neurocytoma) 

Molecular biology: 

- 1p and 19q codeletion - marker of response to chemotherapy and radiation and thus better prognosis. More characteristic of oligodendroglioma (vs astrocytoma) 

- Intact 1p/19q: worse response to chemo/RT

Path 

- fried egg appearance - round nuclei with halos (retraction artifact?)
- in background of normal neurons - infiltrating cells
- can occur with fine/small branching capillaries giving it a "chicken wire" appearance

Imaging: 
- Usually calcified (70-90% calcified)
- Sometimes focally hemorrhagic. Sometimes (20%) cystic.

(source: radiopaedia) 

- CT bright: calcifications or hemorrhage, may erode overlying skull 

- T1 dark, T2 bright 

- Minimal peritumoral edema

- May enhance, enhancement usually heterogenous 

- These tumors typically go all the way to the outer cortex of the brain