MICROSCOPIC DESCRIPTION:
The sections show densely hypercellular tissue fragments composed of a mixture of CD68+ monocyte macrophages and astrocytic cells which show moderate to marked nuclear and cellular pleomorphism. Both cell types are arranged in diffuse sheets. There is prominent microvascular proliferation with multilayering of endothelial cells which also show nuclear and cellular pleomorphism. Endothelial cell mitoses are noted.
There are a moderate number of Creutzfeldt astrocytes. Mitotic figures are identified in atypical atrocytic cells. A fragment of necrotic tissue is present with neutrophilic infiltration of the immediately adjacent viable tissue. Collections of CD3+ lymphocytes are noted within and adjacent to the walls of some blood vessels. Extensive loss of myelin is identified in a Luxol Fast Blue stained section and granular LFB+ material is seen in the cytoplasm of macrophages. Preservation of axons is seen in a Bodian stained section.
IMMUNOHISTOCHEMISTRY:
- GFAP positive in atypical and reactive astrocytes and
- Creutzfeldt cells.
- Nestin positive
- IDH-1 negative
- p53 positive
- p16 negative
Topoisomerase labelling index: Approximately 12%
FINAL DIAGNOSIS:
Left temporal lesion: Features favouring glioblastoma multiforme (WHO Grade IV)
COMMENT:
These are difficult biopsies to interpret with apparent overlapping features of demyelination (loss of myelin on Luxol Fast Blue staining, axonal preservation, perivascular T lymphocyte aggregation; the presence of Creutzfeldt astrocytes) and high-grade astrocytoma (astrocyte pleomorphism, mitotic figures, microvascular proliferation and necrosis).
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 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 tumours (2016).