Dysembryoplastic neuroepithelial tumour (atypical)
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Well circumscribed left temporal lobe cortical tumour with prominent contrast enhancement and a minor amount of surrounding oedema is present.
The patient went on to have a craniotomy and resection.
Paraffin sections show cerebral cortex and white matter. Within the cortex and extending for a short distance into white matter are relatively circumscribed hypercellular areas composed of cells with round and oval hyperchromatic nuclei, many with peri-nuclear clearing.
Formation of glioneuronal element-like structures and occasional mature neurones within spaces between these structures are noted. No mitotic figures, microvascular proliferation or necrosis are seen. The cells show strong immunostaining for synaptophysin and Nogo A and weaker staining for GFAP. There is patchy, moderate nuclear staining for p53. No staining for IDH-1 is seen. The topoisomerase labelling index is approximately 1%. Mild dysplastic features in the form of large neurones in lamina I and malorientation of neurones in deeper laminae are also noted.
FISH shows no loss of either chromosome 1p or chrommosome 19q.
Low grade glioneuronal lesion with features most consistent with dysembryoplastic neuroepithelial tumour (DNET)
This is an unusual lesion and it would be difficult to make a pre-operative diagnosis on imaging alone. The presence of intense enhancement would make DNET less likely, favouring gangliglioma or pleomorphic xanthastrocytoma. Small foci of signal loss, if calcificaiton would further argue against DNET, favoring ganglioglioma over the other diagnoses.
Pathology is also not absolutely conclusive.