The patient went on to have surgery.
Histology
MICROSCOPIC DESCRIPTION:
The sections show features of a moderately cellular glial tumour. The tumour cells form sheets and there are widely distributed perivascular pseudorosettes, where the tumour cells surround central blood vessels. No thick radiating astroblastic type cytoplasmic processes are seen. A few blood vessels are hyalinised. The background is fibrillary. The tumour cells have angulated and hyperchromatic nuclei. Some fascicular arrangement is noted, with a tanycytic-like pattern. No Rosenthal fibres or eosinophilic granular bodies are noted. There are 2 mitoses per 10 high-power fields. No microvascular proliferation is seen. There are occasional foci of non-palisaded necrosis where there is fibrinoid material and some neutrophils. No oligodendroglial component is noted. The features are those of ependymoma.
The tumour cells are GFAP, CD99 and focally p53 positive. The topoisomerase index is about 5%. IDH1-R132H immunostain is negative. MGMT is positive (likely unmethylated). ATRX shows no loss of staining (non-mutated). EMA shows scattered positive cells with a perinuclear dot pattern of reactivity. A few rudimentary ependymal canal-like structures are noted. NeuN and synaptophysin are negative, excluding neurocytoma.
FINAL DIAGNOSIS: Ependymoma (WHO Grade II).