Glioblastoma IDH wild-type (with dural tail)
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A peripherally-based contrast-enhancing mass, involving the cortex and abutting the dura, which is smoothly thickened. Mild diffusion restriction has developed at the medial margin of the mass. The mass demonstrates elevated cerebral blood volume.
On spectroscopy, a voxel anterior to the contrast enhancement demonstrates elevated choline-to-creatine and increased lactate. There is increased local mass effect; however, no midline shift.
Additionally a right parietal parafalcine extra-axial, vividly enhancing mass is stable. It invades the superior sagittal sinus and extends into an overlying diploic space.
Elsewhere, scattered foci of FLAIR hyperintensity are in keeping with chronic small vessel ischaemia.
The patient went on to have a craniotomy and excision. Histology report:
An irregular piece of soft tan and dark brown tissue 30x28x11 mm with an attached triangular sheet of rubbery tan dura 55x40mm.
Paraffin sections show a densely hypercellular astrocytic glioma. Tumour cells have predominantly fibrillary features and show moderate nuclear and cellular pleomorphism. Frequent mitotic figures are identified. There is microvascular proliferation and areas of both palisaded and confluent necrosis are also seen. Many of these incorporate thin-walled necrotic and thrombosed blood vessels.
Tumour extends along overlying dura from which it is variably separated by a layer of hyperplastic arachnoidal cells.
- GFAP positive
- Nestin positive
- IDH-1 R132H negative (not mutated)
- MGMT negative (likely methylated)
- p16 negative
- p53 negative
- Topoisomerase labelling index: Approximately 30%
FINAL DIAGNOSIS: Glioblastoma
The patient went on to have a craniotomy and excision. A glioblastoma (WHO Grade IV) was histologically diagnosed.
Most basic radiology textbooks teach that the dural tail sign is pathognomonic of an extra-axial dural-based mass. This is simply not the case! Intra-axial cortical lesions can induce dural thickening that manifests as a dural tail. In addition to glioblastoma (as in this case), metastases and other primary tumours (e.g. pleomorphic xanthoastrocytoma) can give this appearance, as well as peripherally located infections.
Note: The diagnosis of glioblastoma IDH wild-type is actually not entirely established in this case as the IDH wild-type status has only been inferred with a negative IDH1 R132H immunohistochemistry. Although it is in principle possible that this is a non-R132H mutation or an IDH2 mutation, in an elderly individual +/-[particularly with unmethylated MGMT] this possibility is remote.