The patient went on to have surgery.
MICROSCOPIC DESCRIPTION: Sections show a hypercellular spindle cell tumour with prominent haemangiopericytomatous "staghorn" blood vessels. Tumour cells are arranged in solid sheets containing abundant pale eosinophilic cytoplasm, elongate oval moderately pleomophic nuclei with coarse chromatin and inconspicuous nucleoli. Focally the tumour demonstrates myxoid degeneration (specimen 5). No sarcomatous elements, necrosis or atypia is seen. There are up to 9 mitoses per 10 hpf identified.
Immunohistochemical results show tumour cells stain: CD34+ (focal), BCL2+, CD99+, STAT6+ (focal), EMA- and PgR-. The Topoisomerase proliferation index is approximately 5-10%.
Haemangiopericytoma with anaplastic features (WHO grade III).
NB: as of the 2016 update to the WHO classification of CNS tumours, haemangiopericytomas are considered part of a spectrum along with solitary fibrous tumour of the dura.