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Ganglioglioma

Case contributed by Bruno Di Muzio
Diagnosis certain

Presentation

Long history of temporal lobe epilepsy.

Patient Data

Age: 40 years
Gender: Female

MRI Brain

mri

A small cystic lesion in the inferomedial aspect of the left anterior temporal pole with surrounding T2 hyperintense region of cortical expansion. It demonstrates minimal choline elevation with no NAA depression or lactate peak on spectroscopy. No increase in cerebral blood volume (rCBV). No diffusion restriction with ADC values demonstrating facilitated diffusion in both the cystic and solid cortical components. On the post-contrast sequences, there is the impression of mild enhancement, although, immediately above this level some phase artefact related to the skull base vessels is present.

Remainder the brain is within expected limits.

Conclusion

The imaging features, particularly in this clinical context, suggest a low-grade glioneuronal tumor such as ganglioglioma or DNET.

pathology

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).

Final diagnosis

Ganglioglioma (WHO Grade I).

Case Discussion

The imaging features of many of the long-term epilepsy-associated tumors (LEATs) are overlapping, and distinguishing between some of the (e.g. gangliocytoma versus ganglioglioma) is in most cases not possible. Fortunately, in most instances, a precise preoperative diagnosis is not crucial to patient management as surgical resection (in the correct clinical context) is curative and final diagnosis requires histology, immunohistochemistry and, increasingly, molecular techniques (such as DNA methylation profiling).

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