The patient went on to have a stereotactically guided biopsy.
Histology
MICROSCOPIC DESCRIPTION: Paraffin sections show small fragments of a moderately hypercellular glial tumour. This is composed of a mixture of oligodendroglial and astrocytic cells. Both show mild nuclear pleomorphism. Scattered gliofibrillary oligodendrocytes are also noted. Several mitotic figures are identified and there is microvascular proliferation with multilayering of atypical cell around vessel lumena. No necrosis is seen. Several incorporated neurones containing melanin pigment are also noted.
IMMUNOHISTOCHEMISTRY:
- GFAP positive in tumour and reactive astrocytes and in gliofibrillary oligodendrocytes.
- NogoA positive in tumour oligodendrocytes.
- IDH-1 R132H negative (not mutated / wild-type)
- ATRX positive (not mutated)
- MGMT negative (likely methylated)
- p53 positive in tumour astrocytes p16 negative
- Topopisomerase labelling index: Approximately 20%.
FINAL DIAGNOSIS: IDH-1 wild-type anaplastic oligoastrocytoma - WHO Grade III
NOTE: This case predates the 2016 WHO classification of CNS tumour revision. As no 1p19q co-deletion status is available a formal diagnosis cannot be reached and the NOS is therefore used (not otherwise specified) - which is recognised in the current classification for cases where molecular information is unavailable. It should also be noted, that under the new classification both an astrocytic and oligodendroglial component needs to be identified, each with its own molecular markers. True oligoastrocytomas are therefore going to be rare, and this case would most likely be classified as either an astrocytoma or an oligodendroglioma.