Glioblastoma IDH wild-type (crossing the corpus callosum)
Left upper and lower limb weakness.
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High FLAIR signal in the right frontal lobe, crossing the corpus callosum into the left frontal lobe. Predominantly peripheral contrast enhancement in the region of high FLAIR signal also crosses the corpus callosum; a more discrete contrast enhancing nodule in the left frontal lobe lies within the region of contiguous high FLAIR signal. Within this abnormality there is increased cerebral blood volume and low ADC values of 800-900.
The remainder of the brain is within normal limits.
Findings are in keeping with high grade glioma crossing the corpus callosum.
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Glioblastomas, along with CNS lymphoma, are one of few tumours that cross the midline via the corpus callosum. Cerebral metastases rarely have this pattern of spread.
The patient proceeded to open biopsy.
The sections show features of a densely cellular astrocytic tumour. The tumour cells have elongated, angulated and hyperchromatic nuclei. Scattered mitotic figures are identified. There are foci of microvascular proliferation. Areas of palisaded necrosis are present. The features are those of glioblastoma. The tumour cells are focally p53 and MGMT (about 20%) immunostains positive. There is no loss of ATRX staining. IDH-1 immunostain is negative.
DIAGNOSIS: Brain tumour: Glioblastoma (WHO Grade IV).
Note: Although this tumour 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 tumour in an older individual makes the possibility of this being IDH mutant remote, and sequencing is not felt to be necessary by many institutions.