Presentation
Headache
Patient Data
A large vividly enhancing but heterogeneous mass is seen on the left, abutting / arising form the tentorium and invaginating / extending into the undersurface of the occipital lobe. It is surrounded by cysts. ADC demonstrates facilitated diffusion compared to brain. Prominent flow voids are present.
Case Discussion
The patient went on to have a resection.
Histology
Paraffin sections show a densely hypercellular tumor. Tumor cells have moderately pleomorphic round, oval and angulated vesicular nuclei. Cytoplasmic boundaries are poorly defined. Tumor cells are aggregated in solid sheets with no specific architectural pattern discernible. However, in several areas, small caliber open vascular spaces are noted. These are lined by unremarkable endothelium. A moderately fibrous stroma is noted in several areas of the tumor. A very occasional mitotic figure is identified. There are no areas of necrosis. No evidence of invasion into brain parenchyma is seen.
Immunohistochemistry shows strong staining of tumor cells for CD34 and bcl-2. There is also moderate nuclear staining for progesterone receptor (PgR). No staining for epithelial membrane antigen (EMA), cytokeratin AE1/AE3, GFAP, ALK-1 or tyrosinase is seen in tumor cells. The features are of hemangiopericytoma (WHO Grade II). The topoisomerase labeling index is <1%.
FINAL DIAGNOSIS: solitary fibrous tumor of the dura (previously hemangiopericytoma) - WHO Grade II.
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.
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