Glioblastoma IDH wild-type (multifocal)
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There is confluent T2 / FLAIR hyperintense signal abnormality affecting the corona radiata and the centrum semiovale of the cerebral hemispheres with involvement of the corpus callosum, the right frontal operculum, the hippocampi, to a lesser extent the thalami and the left cerebral peduncle. In the right frontal operculum there is involvement of grey and white matter, and the suggestion of gyral expansion.
Within the centrum semiovale and corpus callosum, there are a number of focal higher T2 / FLAIR hyperintensities with predominantly peripheral irregular enhancement.
There are bilateral confluent T2 hyperintense abnormalities in the cerebral hemisphere with predominantly peripheral irregular areas of contrast enhancement as detailed. Appearance almost certainly represent a multifocal glioblastoma.
The patient went on to have a biopsy.
Paraffin sections show cores of a densely hypercellular astrocytic glioma. Tumor cells show marked nuclear and cellular pleomorphism. Scattered mitotic figures are identified. There are foci of microvascular proliferation with multi-layering of atypical cells around vessel lumena. There is also a small focus of necrosis.
- GFAP: positive
- Nestin: positive (high)
- IDH-1 R132H negative (wild-type - not mutated)
- ATRX: positive (not mutated)
- MGMT: negative (likely methylated)
- p53: positive
- p16: focally positive
- Topoisomerase labeling index: approximately 30%.
FINAL DIAGNOSIS: Multifocal glioblastoma (WHO Grade IV).
Note: Although this tumor is entirely consistent with IDH wild-type molecular subtype, strictly speaking, to conclusively establish this, IDH would need to be sequenced to ensure that a non-IDH1 R132H mutation was present. In practice, an IDH1 R132H negative tumor in an individual over 55-years-of-age makes the possibility of this being IDH mutant remote (<1%), and sequencing is not felt to be necessary by many institutions, and not recommended by the WHO classification of CNS tumors (2016).