The patient went on to have a biopsy.
Histology:
MICROSCOPIC DESCRIPTION:
All the sections show features of a moderately cellular infiltrating glial tumour. The tumour has prominent extension into the cerebral cortex as well as involving the white matter. The tumour cells form aggregates and cords. Many of the tumour cells have features of oligodendrocytes. They have enlarged round nuclei and occasional perinuclear haloes. Smaller numbers of neoplastic cells are more astrocytic with elongated and angulated nuclei. Within the cortex, there is secondary structuring including perineuronal satellitosis and perivascular aggregation. Mitoses are inconspicuous. No microvascular proliferation or necrosis is present. The tumour cells show variable staining for GFAP and Nogo-A, indicating astrocytic and oligodendroglial differentiation respectively. The topoisomerase index is about 1%. IDH-1 immunostain is negative. MGMT stains about 20% of the tumour cells. The features are those of oligoastrocytoma.
FINAL DIAGNOSIS:
Oligoastrocytoma. Based on morphology alone, the tumour would be classified as WHO grade II. However, if the radiology suggests gliomatosis cerebri (by definition, involving at least 3 lobes), then this lesion might possibly behave as a grade III tumour.