Meningeal hemangiopericytoma (historical)

Meningeal haemangiopericytomas are rare tumours of the meninges, often presenting as a large and locally 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 on 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, however these tumours are now known tothen considered to arise from smooth muscle perivascular pericytes of dural capillaries (pericytes of Zimmerman) ^3, but the most recent studies suggesting that these lesion are actually arising from fibroblast and considered in the spectrum of the solitary fibrous tumours ⁴.

They are more aggressive than meningiomas, have a higher frequency of recurrence, and are considered a grade II tumour in the WHO Classification (in contrast to meningiomas which are WHO grade I). Anaplastic haemangiopericytomas are WHO grade III tumours, and have a propensity to metastasise systemically ³. 

Radiographic features

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

Other common location is posterior fossa in posterior occipital region.

CT

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

MRI

• T1: isointense to grey matter
• T1 C+ (Gd)
  • 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
• assessment of dural venous sinus involvement 

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. 

• meningioma
  • older patients (>50 years of age)
  • smoother
  • central vascular spoke-wheel vascular supply
  • less likely to erode adjacent bone
  • more likely to cause hyperostosis
  • more likely to be multiple
  • do not metastasise
  • almost always have a broad dural attachment and dural tail, both of which haemangiopericytomas sometimes lack
  • MRS: alanine peak, absent myo-inositol peak
• solitary fibrous tumour