MICROSCOPIC DESCRIPTION: The sections show a variably hypercellular spindle and epithelioid cell tumour with a broad dural attachment. The tumour is intensely vascular and, in many areas, vessels have "staghorn" profiles. Tumour cells show moderate nuclear pleomorphism and are dispersed in a fibrous stroma. Occasional mitotic figures are identified (3/30HPF). No areas of necrosis are identified. Infiltration into bone is seen in specimen 2. There is no evidence of brain invasion.
Inmmunohistochemistry shows strong staining in tumour cells for bcl-2 and MIC2 (CD99) and moderate staining for CD34. Immunostaining for epithelial membrane antigen (EMA) and progesterone receptor (PgR) is negative.
The features are of solitary fibrous tumour/haemangiopericytoma spectrum tumour (WHO Grade II). The topoisomerase labelling index is approximately 1%.
DIAGNOSIS: Bone/skull/brain tumour: Solitary fibrous tumour/haemangiopericytoma spectrum tumour (WHO Grade II).
SUPPLEMENTARY REPORT: Sections of decalcified tissue show permeation of bone by tumour extending to but not breaching the outer table.