Sections show a moderately cellular tumour composed of moderately pleomorphic cells containing round to oval, hyperchromatic, vesicular nuclei with inconspicuous nucleoli. Tumour cells are arranged in diffuse sheets with microcyst formation. Tumour cells demonstrate perineuronal satellitosis and subpial aggregation.
Occasional mitotic figures are identified (up to 1/1ohpf). No necrosis or microvascular proliferation is seen.
Immunohistochemistry
GFAP: Positive
NogoA: Positive
Nestin: Positive (intermediate)
IDH-l R132H: Positive (mutated)
ATRX: Negative (mutated)
p53: Positive
p16: Negative
Topoisomerase labelling index: Approximately 5%.
Final diagnosis
diffuse astrocytoma, IDH-l mutant (WHO Grade 2).