Presentation
Epilepsy.
Patient Data
There is a 12mm FLAIR hyperintense lesion within the right frontal white matter immediately anterior to the right lentiform nucleus. A tail of abnormal signal extends to the right lateral ventricle frontal horn. No negative mass effect or central cystic component.
A FLAIR hyperintensity mass is also demonstrated within the right mesial temporal lobe, centered in the amygdala. This predominantly involves cortex but extends into the subcortical white matter. No uncal herniation or ventricular compression.
Neither lesion demonstrates enhancement, diffusion restriction, hemosiderin staining or elevated CBV (not shown). Spectroscopy demonstrates elevated choline and decreased NAA in the right mesial temporal lobe. Incidental left frontal developmental venous anomaly.
Conclusion: The right anteromedial temporal lobe mass has features most suggestive of low grade glioma. The right frontal white matter lesion is more indeterminate and may reflect either a further focus of glioma, a developmental lesion or an incidental ischemic/demyelinating focus.
Paraffin sections show a small fragment of edematous brain parenchyma. This contains a population of pleomorphic ganglion cells mixed with reactive astrocytes. No mitotic figures, vascular proliferation or necrosis are seen.
No features of malformation of cortical development are seen. White matter appears of normal cellularity. Myelin is intact. No inflammation is seen and there is no evidence of tumor.
The sections of uncus and hippocampus show a prominent population of pleomorphic ganglion cells. These have a haphazard arrangement. Several binucleate forms are noted. These are admixed with a population of reactive astrocytes. No mitotic figures are identified and there is no vascular proliferation or necrosis.
Immunohistochemistry shows strong nuclear staining for NeuN and strong granular cytoplasmic and membrane staining for synaptophysin in the ganglion cells.
A neoplastic glial component is not demonstrated with immunohistochemistry showing GFAP reactivity in a population of reactive astrocytes, preserved nuclear immunostaining for ATRX and no staining for IDH-1 R132H or p53.
Nuclear staining for topoisomerase is seen in only an occasional cell.
Final diagnosis
Gangliocytoma (WHO Grade I) no features of hippocampal sclerosis seen.
Case Discussion
Gangliocytomas are rare benign (WHO grade I) CNS tumors which differ from gangliogliomas by the absence of neoplastic glial cells. Both tumors are defined by the presence of displaced ganglion cells (large mature neurons that show cytological or architectural abnormalities).
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