Hemangiopericytoma, WHO Grade II
There is a mildly heterogeneous extra-axial mass in the left lateral posterior fossa, demonstrating intermediate T1- and T2-signal intensity. Upon contrast administration, the mass enhances avidly and prominent vascularity is identified within and around the mass. On diffusion-weighted imaging (DWI, not shown here), there is no restricted diffusion. The mass demonstrates a broad abutment of the adjacent tentorium, with an extension of the tumor into the left sigmoid sinus. The mass causes compressive deformation of the underlying cerebellar hemisphere and left dorsolateral brain stem, resulting in mild vasogenic edema. The fourth ventricle is distorted, with no hydrocephalus.
The typical presentation for hemangiopericytomas mimics that of meningiomas, including headache and dizziness. Hemangiopericytomas most commonly present in the fourth to sixth decade. While clinical and radiologic differentiation of meningiomas and hemangiopericytomas can be difficult, hemangiopericytomas are a distinctive mesenchymal neoplasm arising from the pericytes surrounding capillaries, which is unrelated to meningiomas. Differentiation, however, is important as recurrence rate and metastases are much more common with hemangiopericytomas.
On CT, hemangiopericytomas tend to be heterogeneous, dense, and dural based. Differentiating features that would suggest a hemangiopericytoma over a meningioma include bone erosion, narrow dural attachment, irregular or lobulated borders, apparent parenchymal invasion, and more heterogeneous enhancement, consistent with their more aggressive nature.
On MR, hemangiopericytomas tend to be heterogeneous, though predominantly isointense on T1 and T2 images. It is common to have surrounding edema and mass effects. Prominent internal flow voids and heterogeneous contrast enhancement can help suggest hemangiopericytoma over meningioma.
- Chiechi MV, Smirniotopoulos JG, Mena H. Intracranial Hemangiopericytomas: MR and CT Features. AJNR Am J Neuroradiol. 1996;17:1365-1371.
- Wu W, Shi J, Cheng H, et al. Hemangiopericytomas in the Central Nervous System. J Clin Neurosci. 2009;16:519-523.