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In the medial left anterior temporal lobe is an area of abnormality characterized by T2 hyperintense cortical and subcortical expansion with an internal cystic focus and a few tiny cystic foci towards the periphery of the lesion. This lesion contains susceptibility artefact compatible with blood product or calcification. Post contrast sequences demonstrate minor enhancement. No diffusion restriction. MRS demonstrates minimal choline elevation with no NAA depression or lactate peak on spectroscopy. No cerebral blood volume (CBV) increase.
The remainder of the brain demonstrates abnormal T2 signal with no diffusion restriction or susceptibility artefact. The hippocampal formations are normal and symmetric in size, signal and architecture.
Conclusion: T2 hyperintense expansile lesion in the medial left anterior temporal pole containing cystic areas and foci of susceptibility artefact. This is likely to be a low-grade glial tumor such as a ganglioglioma or a DNET.
The patient went on to have surgery.
MICROSCOPIC DESCRIPTION: All the sections contain tumor which is moderately cellular. The glial cells have elongated, angulated and hyperchromatic nuclei. Some fascicular arrangement is noted. Scattered dysmorphic neurons are seen, intermixed with the glial cells. They are haphazardly arranged. Some are binucleated. They have nucleomegaly. Mitoses are inconspicuous. No microvascular proliferation or necrosis is present.
Occasional eosinophilic granular bodies are noted. There is no oligodendroglial component. The adjacent cortex shows cortical dysplasia with disorganized neurons but no balloon cells (FCD Type IIIb). Some of the tumor cells are GFAP positive and other cells NeuN and synaptophysin positive, indicating both glial and neuronal differentiation. IDH-1 and MGMT are negative.
The topoisomerase index is 1-2%. ATRX shows no loss of staining (non-mutated). The features appear to show a low grade glioneuronal tumor, consistent with a ganglioglioma.
Low grade glioneuronal tumor, consistent with a ganglioglioma (WHO Grade I).