Specific Imaging Findings

Hemangiopericytoma (HPC) simulates the imaging appearance of meningioma, as they are both meningeal-based neoplasms, occur in the same extra-axial locations, and show marked enhancement with contrast, frequently with a dural tail. The tumors are hyperdense or heterogenous on CT scans and do not lead to hyperostotic changes in the adjacent bone, whereas bone erosions are frequently present. HPCs are usually T1 isointense and of high or mixed intensity on T2-weighted MR images, homogeneously or heterogeneously enhancing, with the solid portions being dark on ADC maps, reflecting low diffusion of water. This combination of high T2 signal and low ADC values is unusual for a typical meningioma and is suggestive of a higher-grade meningioma or HPC. The distinguishing feature of HPC is the presence of intratumoral flow-voids (reflecting its extremely high vascularity), which is at times striking but frequently much more subtle, especially in small tumors.

Pertinent Clinical Information

The presenting symptoms of HPC are nonspecific, most commonly headache and seizures. Treatment with gross total resection provides the greatest survival advantage. These tumors are very aggressive with a tendency for recurrence and extracranial metastatic spread, sometimes after a prolonged symptom-free interval, frequently many years later. They usually occur in adults, whereas rare HPCs in infants have a better response to chemotherapy and overall prognosis.

Differential Diagnosis

Meningioma (138, 203)

1. • intratumoral flow-voids are very unusual

2. • destruction of the adjacent bone is very unusual

3. • may be indistinguishable