A pathologically proven case of hemangiopericytoma.

Histopathology

A vascular neoplasm is composed of mild atypical cells with vesicular nuclei, visible nucleoli, eosinophilic and focal clear cytoplasm and stag-horn like intratumoral blood vessels arranged in sheet-like features. No necrosis is seen. Few mitotic figures (up to 3/10 HPF) are noted. Foci of eosinophilic collagenous bands are evident.

IHC study revealed:

• CD34: Positive
• CD117: Positive
• CD99: Positive
• Vimentin: Non specific
• EMA: Negative
• PR; Negative
• S100: Negative
• GFAP: Negative
• Ki 67: Up to 2-3%

FINAL DIAGNOSIS: solitary fibrous tumor of the dura (previously hemangiopericytoma)

Note: Due to molecular/genetic similarities hemangiopericytomas are no longer recognized as distinct entities. Instead, they represent cellular higher-grade solitary fibrous tumors. In the 2016 revised 4th Edition of the WHO classification of CNS tumors, they were grouped together under one diagnosis (solitary fibrous tumor/hemangiopericytoma), and in the 2021 5th edition the term hemangiopericytoma was dropped entirely.