Diffuse astrocytoma NOS
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MRI of the brain demonstrates a region of increased T2 signal with positive mass effect involving the superior frontal gyrus. A faint region of contrast enhancement is present.
Features are consistent with a diffuse low-grade glioma. Only faint enhancement and absence of evidence of necrosis/haemorrhage argues against a higher grade lesion (i.e unlikely to be a GBM).
Paraffin sections show fragments of white matter. These show a moderate increase in the numbers of astrocytic cells and prominent perineuronal and perivascular secondary structuring. Astrocytic cells show a mild degree of nuclear atypia and there is clustering of cells in many areas. No mitotic figures are seen and there is no vascular endothelial cell proliferation and no necrosis. A minority of atypical astrocytic cells show strong nuclear staining for Ki-67/MIB-1 (proliferation index approx. 5%). The features are of diffuse fibrillary astrocytoma.