The patient went on to have a resection. 

Histology: 

Sections show a markedly cellular glioma with a discrete border with adjacent gliotic brain. The tumor cells are predominantly monomorphic malignant cells oval nuclei, fine nuclear chromatin and pale eosinophilic cytoplasm. The cells are arranged into sheets as well as palisading along the edge of cystic spaces. There are prominent ependymal canals and pseudorosettes. Mitoses are frequent (5 per 10 high power fields). There is abundant non-palisading necrosis and microvascular proliferation is seen. Scattered foci showing marked cytological atypia and present.

Immunohistochemistry:

• EMA positive
• CD99 positive
• M2A positive
• S100 positive
• GFAP positive
• IDH1 R132H negative
• Ki67 index = ~30%
• P53 positive
• ATRX - positive (not mutated)

FINAL DIAGNOSIS: Anaplastic supratentorial parenchymal ependymoma (WHO Grade III).