Glioblastoma IDH wild-type (with primitive neuronal component)
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There is a right frontal lesion, with mixed cystic and solid components. Intense irregular rim-like enhancement pattern is seen, as well as enhancement of the solid component. Areas of moderate restriction diffusion are seen within the lesion, corresponding to the solid components (not the fluid / non-enhancing component).
Multiple flow voids are seen within the lesion.
There is a significant amount of surrounding flair signal abnormality, with 13 mm leftward midline shift at the level of the septum pellucidum.
Findings are most likely in keeping with a high-grade astrocytoma (WHO grade IV).
The patient went on to have surgery.
Paraffin sections show a densely hypercellular tumor. This is composed almost entirely of cells with features of primitive neuroectoderm with overlapping angulated hyperchromatic nuclei and a paucity of processes. These are arranged in diffuse sheets. In some very small areas, fibrillary astrocytic and oligodendroglial morphologies are discernible. Frequent mitotic figures are identified and there is prominent microvascular proliferation with florid endothelial cell hyperplasia. Many areas of palisaded and confluent necrosis are also identified. Several of these incorporate thin-walled necrotic and thrombosed blood vessels. The features are of glioblastoma multiforme with a large primitive neuroectodermal tumor (PNET) component (WHO Grade IV).
- GFAP positive
- Synaptophysin patchy positive
- Nestin positive
- IDH-1 R132H negative (not mutated)
- MGMT negative (likely methylated)
- p53 negative
- p63 negative
- Topoisomerase labeling index: Approximately 35%
Glioblastoma with a large primitive neuronal component (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). In a younger patient (like this one) sequencing would be recommended. Thus the diagnostic certainty has been dropped to "almost certain".
Note: The current (2016) WHO classification of CNS tumors has made substantial changes to tumors previously considered to be PNET, now classified as embryonal tumors with multilayered rosettes (ETMR). In contrast, when a glioblastoma demonstrates similar histological features it is now referred to as a glioblastoma with primitive neuronal component