Pathology
H&E
H&E
H&E
MICROSCOPIC DESCRIPTION: The sections show fragments of unremarkable cerebral cortex and white matter and separate fragments of a densely hypercellular glial tumour. Tumour cells are a mixture of pleomorphic, astrocytic and oligodendroglial cells arranged in diffuse sheets. Scattered mitotic figures are identified and there are several foci of microvascular proliferation with multilayering of atypical cells around vessel lumena. Scattered small foci of necrosis are also seen.
IMMUNOHISTOCHEMISTRY: GFAP positive in tumour astrocytes; negative in oligodendroglial cells Nogo A positive in tumour oligodendrocytes; negative in tumour astrocytes. Nestin positive (high) IDH-1 R132H negative (not mutated) ATRX negative (likely mutated) MGMT negative (likely methylated) p53 negative p16 negative Topoisomerase labelling index: Approximately 35% The features are of glioblastoma multiforme with an oligodendroglioma component (WHO Grade IV).
DIAGNOSIS: Brain tumour: Glioblastoma multiforme with an oligodendroglioma component (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 individual of 50-years-of-age the possibility of this being IDH mutant low. Generally, it is felt that sequencing is unnecessary over the age of 55 as the rate of non-R132H mutations is <1%, and not recommended by the WHO classification of CNS tumours (2016).