Diagnosis:
Suggested by MRI and confirmed by pathology (brain biopsy/resection)
Pathology:
Histology: small round blue nucleus, halo of cytoplasm ‘fried egg or honey comb’ appearance on formalin fixed tissue. Thin walled branching capillaries ‘chicken wire or wishbone’ appearance. Minigemistocytes, perineuronal satellitosis & Microcalcifications may occur. In higher grade; endothelial proliferation, mitosis & necrosis are present.
Immunohistochemistry: GFAP classic cells are negative, minigemistocytes are positive, some cells have a perinuclear rim= gliofibrillary oligodendrocytes. S100 positive. The following are negative: CLA, Cytokeratins, EMA, HMB45.
FISH: deletion of 1q & 19p.
Findings on Investigations:
Involvedment of the frontal lobes or temporal lobes. Rare in spinal cord, brain stem & posterior fossa
CT:
- hypodense mass, serpentine calcification, cystic areas. Hemorrhage can occur. Usually no oedema. Variable enhancement
MRI:
- T1: hypointense
- T2/FLAIR: hyperintense tumor, hypointense calcification. But calcification is easier to see on CT
Treatment:
Oligodendroglioma:
- Surgical resection
- Consider Chemotherapy:
- Procarbazine +Lomustine CCNU+Vincristine PCV if 1p/19q deletion. Increases progression free survival PFS but doesn’t increase overall survival. Toxicity overweighs benefit in grade III.
- Temozolamide TMZ if 1p/19q codeletion & low grade (200 mg/m2/day for 5 consecutive days, repeated every 28 days).
Mixed Oligoastrocytoma, WHO grade II & grade III:
If grade II:
- Surgical resection
- Consider Chemotherapy: Temozolamide TMZ if 1p/19q codeletion (200 mg/m2/day for 5 consecutive days, repeated every 28 days).
If grade III:
- Surgical resection
- Consider radiotherapy