MICROSCOPIC DESCRIPTION: The sections show cerebral cortex and white matter. Cortical laminar architecture is preserved with no features of cortical dysplasia seen. There is prominent perineuronal secondary structuring. White matter contains a population of atypical glial cells with oligodendroglial morphological features - enlarged round and oval hyperchromatic nuclei, some with perinuclear clearing and a paucity of processes. Several groups of overlapping nuclei are noted. No mitotic figures are identified. There is no microvascular proliferation and no necrosis is seen. A population of reactive astrocytes is also present.
IMMUNOHISTOCHEMISTRY: GFAP negative in atypical oligodendroglial cells; positive in reactive astrocytes. NogoA positive in atypical oligodendroglial cells. IDH-1 R132H positive (mutated) ATRX positive (not mutated) p53 negative MGMT positive (likely unmethylated) p16 CDKN2A positive Topoisomerase labelling index: Approximately 1%. The features are of IDH-1 mutated diffuse glioma (WHO II) strongly favouring oligodendroglioma.
DIAGNOSIS: IDH-1 mutated diffuse glioma (WHO II) with features strongly favouring oligodendroglioma.