Microscopic diagnosis:
Solitary fibrous tumor (previously known as hemangiopericytoma) with foci of high mitotic activity and necrosis compatible with anaplastic transformation. WHO grade III.
Bone invasion is noted.
IHC result:
- EMA: Negative
- CD34: Positive in endothelial cells
- CD 99: Weakly positive
- Ki-67: Positive in up to 4% of tumor cells
Findings are consistent with hemangiopericytoma with focal anaplastic transformation, WHO grade III.
Note: at the time of diagnosis/case contribution this tumor was known as a hemangiopericytoma. Under the 5th Edition (2021) of the WHO classification of CNS tumors, it is now considered a solitary fibrous tumor of the dura.