Glioblastoma IDH wild-type (multifocal)
The patient went on to have a biopsy.
Paraffin sections show cores of a densely hypercellular astrocytic glioma. Tumor cells show marked nuclear and cellular pleomorphism. Scattered mitotic figures are identified. There are foci of microvascular proliferation with multi-layering of atypical cells around vessel lumena. There is also a small focus of necrosis.
- GFAP: positive
- Nestin: positive (high)
- IDH-1 R132H negative (wildtype - not mutated)
- ATRX: positive (not mutated)
- MGMT: negative (likely methylated)
- p53: positive
- p16: focally positive
- Topoisomerase labeling index: approximately 30%.
FINAL DIAGNOSIS: Multifocal glioblastoma, IDH-wildtype (WHO CNS Grade 4).
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.