Presentation
Syncopal episodes.
Patient Data
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The lesion in the left medial cranial fossa has broad contact with the cranial vault, but there is no reaction the adjacent bone and no meningeal enhancement. There is no evidence of cortex or CSF cleft between the lesion and deep white matter, confirming intra-axial site. There is no contrast enhancement. There is no diffusion restriction. Cerebral parenchymal signal intensity and architecture are elsewhere normal. There is no hydrocephalus.
There is abnormal signal within the left globe consistent with silicon oil injection for the treatment of prior retinal detachment.
Conclusion: The tumor is almost certainly a diffuse astrocytoma IDH+ve and unlikely to have 1p19q deletion given prominent partial flair suppression. An outside possibility is a large DNET although this is much less likely.
MICROSCOPIC DESCRIPTION: 1-2. Sections show a moderately cellular tumor composed of moderately pleomorphic cells containing round to oval, hyperchromatic, vesicular nuclei with inconspicuous nucleoli. Tumor cells are arranged in diffuse sheets with microcyst formation. Tumor cells demonstrate perineuronal satellitosis and subpial aggregation.
Occasional mitotic figures are identified (up to 1/1ohpf). No necrosis or microvascular proliferation is seen.
IMMUNOHISTOCHEMISTRY RESULTS:
- GFAP: Positive
- NogoA: Positive
- Nestin: Positive (intermediate)
- IDH-l R132H: Positive (mutated)
- ATRX: Negative (mutated)
- p53: Positive
- p16: Negative
- Topoisomerase labeling index: Approximately 5%.
DIAGNOSIS: 1-2. Brain, left temporal lobe tumor: Diffuse astrocytoma, IDH-l mutant (WHO Grade II).
Case Discussion
The imaging appearances of this left temporal lobe tumor are those of a low-grade glioma, with typical features of what use to be called protoplasmic astrocytoma before the 2016 update on the WHO classification of CNS tumors, a subtype of diffuse astrocytomas that is no longer recognized as a distinct entity. Nowadays, diffuse astrocytomas are divided into two molecular groups according to their IDH status:
This case has been confirmed as an astrocytic tumor IDH-1 mutated and ATRX mutated, making the final diagnosis of a diffuse astrocytoma IDH-1 mutant. Remember that ATRX loss/mutation and 1p19q co-deletion are essentially mutually exclusive, which means that ATRX mutated = no 1p19q co-deletion.
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