Solitary fibrous tumour (haemangiopericytoma)

Case Discussion

This patient went on to have a resection which confirmed the diagnosis. 

Histology

Microscopic Description: 

Sections show a highly cellular vascular neoplasm which appears to be adherent to dura matter. Numerous large thin-walled vascular channels are seen and there is a complex network of delicate small vascular sinusoids. In some areas, the tumour cells are separated by a collagenous stroma but in other regions they form more solid sheets. 

Cellular morphology varies from one region to another. In some areas, the tumour cells have plumped oval nuclei and a relatively delicate chromatin resembling meningioma. In other regions, the nuclei are smaller, angulated and hyperchromatic and the cells have a spindle-cell morphology. 

Cells with clear vacuolated cytoplasm are present and there are focal collections of multinucleate giant cells. The tumour cells have prominent nucleoli and mitotic activity is easily identified. Many areas of the tumour show abundant reticulin deposition which often forms delicate deposits outlining individual tumour cells. There is strong immunoreactivity for vimentin but no reaction for cytokeratin and EMA.

Final diagnosis: solitary fibrous tumour (previously haemangiopericytoma)

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.