Sections show a hypercellular tumour composed of moderately pleomorphic cells containing round to oval, hyperchromatic, vesicular nuclei with inconspicuous nucleoli and prominent perinuclear clearing. Tumour cells are arranged in diffuse sheets intersected by thin-walled "chicken-wire" capillaries. Abundant tumour microcalcification is present. No necrosis or microvascular proliferation is seen. Extracellular non-refractile foreign material and haemorrhage are present, consistent with recent surgery.
- IDH-1 R132H mutation: positive
- 1p19q: co-deleted
FINAL DIAGNOSIS: oligodendroglioma (WHO Grade II).