The patient went on to have surgery.
Histology
Paraffin sections show fragments of a moderately hypercellular glial tumour involving cortex and white matter. Tumour cells have predominantly fibrillary astrocytic morphology with moderate nuclear and cellular pleomorphism. An occasional mitotic figure is identified. There is no microvascular proliferation and no necrosis is identified. A background population of morphologically unremarkable neurones is noted. No bi-nucleate forms are identified.
IMMUNOHISTOCHEMISTRY:
GFAP positive
Nestin negative
Nogo A positive in native oligodendrocytes
IDH-1 R132H negative (not mutated)
ATRX positive (not mutated)
MGMT negative (likely methylated)
p53 negative
p16 CDKN2A positive
Topoisomerase labelling index: Approximately 5%.
Final diagnosis
IDH-1 R132H wild-type diffuse astrocytoma (WHO Grade II).
Note
This case predates the 2021 WHO classification of CNS tumours; you can tell by the use of Roman numerals to indicate grade. The patient is over 55 years of age and thus sequencing to identify non-R132H IDH mutations is not mandatory as the likelihood of identifying one is very low. Thus, using the current classification this would be considered a molecular glioblastoma despite the low histological grade.