Meningeal hemangiopericytoma (historical)

Meningeal haemangiopericytomas are rare tumours of the meninges, often presenting as a large and accountlocally aggressive dural mass, frequently extending through the skull vault. They are difficult to distinguish from the far more common meningioma, but are treated similarly with surgical resection with or without radiotherapy to reduce the risk of recurrence, which is high. 

For a general discusion of non-meningeal haemangiopericytomas please refer to the general article: haemangiopericytoma.

Epidemiology

Haemangiopericytomas account for less than 1% of all intracranial tumours ¹. They are typically encountered in younger adults (30s-40s) with up to 10% being diagnosed in children ³. Slight male predilection (M:F 1.4:1) ³. 

Clinical presentation

As these tumours are typically large, usually supratentorial, presentation is due to mass effect and will vary depending on location. Headache, seizures, focal neurological dysfunction may all be presenting features ³. Additionally these tumours (particularly anaplastic haemangiopericytomas) can metastasize systemically, typically to liver, lung and bone ^1,3.

Pathology

Haemangiopericytomas were previously classified as angioblastic sub-type meningiomas. These, however these tumours are now known to arise from smooth muscle perivascular pericytes of dural capillaries (pericytes of Zimmerman)³.

They are more aggressive than meningiomas, have a higher frequency of recurrence, and are considered a grade II tumour in the WHO Classification (c.f(in contrast to meningiomas which are WHO grade I for  meningioma). AdditionallyAnaplastic haemangiopericytomas are WHO grade III tumours, and again unlikehave a meningioma, they can metastasizepropensity to metastasise systemically ¹³.

Radiographic features

DistinguishingHaemangiopericytomas are almost always solitary, usually supratentorial masses, often lobulated in contour. They are highly vascular and have a tendency to erode adjacent bone ³. 

CT

• vivid enhancement
• erosion of adjacent bone
• no hyperostosis
• no calcification

MRI

• T1: isointense to grey matter
• T1 C+:
  • vivid enhancement
  • heterogeneous
  • may have a narrow base of dural attachment
  • dural tail sign is seen, more commonly in grade II tumours
• T2: 
  • isointense to grey matter
  • multiple flow voids on MRI (need to distinguish from spoke-wheel appearance of meningioma)
  • adjacent brain oedema frequently present
• MRS
  • high myo-inositol ³
  • absent alanaine peak (present in meningiomas) ³
• DWI
  • intermediate restricted diffusion (less than meningioma) 
  • minimum ADC ~ 1100 (+/- 130) x 10^-6 mm²/s 

Angiography

• ECA, ICA and vertebral supply common
• highly vascular
• corkscrew arteries
• fluffy tumour stain
• lack of early draining veins ³
• useful for pre-operative embolisation

Treatment and prognosis

Total surgical excision is recommended, with pre-operative catheter embolisation helpful in limiting blood loss ³. Adjuvant radiotherapy to reduce the incidence of recurrence has also been advocated ^1,3. 

Differential diagnosis

The main differential diagnosis is that of menigioma although all other dural masses should be considered. Distinguishing a haemangiopericytoma from a meningioma can be difficult as they have similar appearances on both CT and MRI. Helpful features include :

• meningioma
  • lobulated contourolder patients (>50 years of age)
  • absence of calcification andsmoother
  • central vascular spoke-wheel vascular supply
  • less likely to erode adjacent bone
  • more likely to cause hyperostosis
  • invasion of the skull (common)more likely to be multiple
  • multiple flow voids on MRI (need to distinguish from spoke-wheel appearance of meningioma)do not metastasise
  • corkscrew arteries
  • mayalmost always have a narrow base ofbroad dural attachment and dural tail, both of which haemangiopericytomas sometimes lack
  • MRS: alanine peak, absent myo-inositol peak

  Treatment and prognosis

  Total surgical excision is recommended, with adjuvant radiotherapy to reduce the incidence of recurrence.

  Differential diagnosis

  • meningioma

  See also

  • haemangiopericytoma - general article