Diagnosis: Oligodendroglioma
• Oligodendrogliomas are diffusely infiltrating gliomas usually present in adulthood and most often in the cerebral hemispheres (predominantly in the frontal lobes).
• Oligodendrogliomas are composed of uniform cells with round nuclei and perinuclear halos (“fried egg” appearance) on paraffin sections. Microcystic degeneration and dystrophic calcifications can be present. A delicate vasculature consisting of branching capillaries runs through the neoplasm (“chicken-wire”).
• Increase in mitotic activity and presence of microvascular proliferation indicate a more aggressive behavior consistent with an anaplastic oligodendroglioma, WHO grade III. Absence of these features, as well as necrosis, is compatible with a WHO grade II oligodendroglioma.
• Concurrent deletion of chromosomal arms 1p and 19q is a hallmark alteration in oligodendrogliomas. This genetic signature is associated with both prolonged survival time and a favorable response to various chemotherapy agents or radiation therapy.
• Favorable prognostic indicators for oligodendrogliomas include young age, WHO grade 2, less than 5% ki-67 labeling index, and 1p/19q loss.
