Pathology
Figure 1
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Figure 3
Figure 4
Slides of a solitary fibrous tumour (previously haemangiopericytoma) demonstrate a highly cellular tumour with sparse background reticulum and numerous branching thin-walled vessels and frequent mitoses. Areas of necrosis are visible (figure 4). This is consistent with a grade III haemangiopericytoma pattern tumour.
Ideally, the diagnosis would be confirmed with STAT6 immunohistochemistry, as well as CD34 and vimentin.
Note: Due to molecular/genetic similarities haemangiopericytomas are no longer recognised as distinct entities. Instead, they represent cellular higher-grade solitary fibrous tumours. In the 2016 revised 4th Edition of the WHO classification of CNS tumours, they were grouped together under one diagnosis (solitary fibrous tumour/haemangiopericytoma), and in the 2021 5th edition the term haemangiopericytoma was dropped entirely.