Meningeal hemangiopericytomas are rare tumors of the meninges, now considered to be aggressive versions of solitary fibrous tumors of the dura, often presenting as a large and locally aggressive dural mass, frequently extending through the skull vault. They are difficult to distinguish on imaging 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 discussion of non-meningeal hemangiopericytomas please refer to the general article on hemangiopericytoma.
Hemangiopericytomas account for less than 1% of all intracranial tumors 1. They are typically encountered in younger adults (30-50 years) with up to 10% being diagnosed in children 3. There is a slight male predilection (M:F 1.4:1) 3,6.
Clinical presentation is usually due to mass effect and will vary depending on location. Headache, seizures, focal neurological dysfunction may all be presenting features 3. Additionally, in up to 20% of cases, these tumors can metastasize systemically, typically to liver, lung and bone 1,3,6.
Hemangiopericytomas were previously classified as angioblastic sub-type meningiomas, then considered to arise from smooth muscle perivascular pericytes of dural capillaries (pericytes of Zimmerman) 3, but the most recent studies suggest that these lesions are actually arising from fibroblast and are in the spectrum of the solitary fibrous tumors of the dura 4. This is further supported by the fact that both entities share a similar genetic alteration: genomic inversion of 12q13 locus resulting in the fusion of NAB2 and STAT6 genes, the latter expressed and able to be assessed using immunohistochemistry techniques 6. In fact, in the 2016 update to the WHO classification of CNS tumors, the two entities have been combined 5.
Solitary fibrous tumors of the dura are WHO I grade one lesion, whereas hemangiopericytomas are WHO grade II or III (anaplastic) tumors 6.
Hemangiopericytomas are highly cellular tumors with frequent mitoses (grade II <5 per 10 HPF; grade III ≥5 per 10 HPF) and often with areas of necrosis 6. The cells are separated by a limited amount of delicate reticulin fibers and have numerous 'staghorn' thin-walled branching vessels, the latter a feature shared by solitary fibrous tumors of the dura 6.
Ideally, the diagnosis is confirmed by assessing for STAT6 expression by immunohistochemistry or identifying NAB2-STAT6 fusion 6. Hemangiopericytomas have a number of useful immunohistochemical markers 6:
- STAT6: positive
- CD34: positive
- vimentin: positive
Ki-67 proliferation index is typically around 10% 6.
Hemangiopericytomas are almost always solitary, usually supratentorial masses, often lobulated in contour. They are highly vascular and have a tendency to erode adjacent bone 3.
Another common location is the posterior fossa in the posterior occipital region.
- vivid enhancement
- erosion of adjacent bone
- no hyperostosis
- no calcification
Features on various sequences include
- T1: isointense to grey matter
T1 C+ (Gd)
- vivid enhancement
- may have a narrow base of dural attachment
- dural tail sign is seen, more commonly in grade II tumors
- isointense to grey matter
- multiple flow voids on MRI (need to distinguish from the spoke-wheel appearance of meningioma)
- adjacent brain edema frequently present
- MR spectroscopy
- intermediate restricted diffusion (less than meningioma)
- minimum ADC ~ 1100 (+/- 130) x 10-6 mm2/s
- ECA, ICA and vertebral supply common
- highly vascular
- corkscrew arteries
- fluffy tumor stain
- lack of early draining veins 3
- useful for pre-operative embolization
- assessment of dural venous sinus involvement
Treatment and prognosis
Total surgical excision is recommended, with pre-operative catheter embolization helpful in limiting blood loss 3. Adjuvant radiotherapy to reduce the incidence of recurrence has also been advocated 1,3.
The main differential diagnosis is that of meningioma although all other dural masses should be considered. Distinguishing a hemangiopericytoma from a meningioma can be difficult as they have similar appearances on both CT and MRI.
- older patients (>50 years of age)
- central vascular spoke-wheel vascular supply
- less likely to erode adjacent bone
- more likely to cause hyperostosis
- more likely to be multiple
- very unlikely to metastasize
- usually, have a broad dural attachment and dural tail
- MRS: alanine peak, absent myoinositol peak
- immunohistochemistry: EMA positive, CD34 and STAT6 negative
- 1. Chiechi MV, Smirniotopoulos JG, Mena H. Intracranial hemangiopericytomas: MR and CT features. AJNR Am J Neuroradiol. 1996;17 (7): 1365-71. AJNR Am J Neuroradiol (abstract) - Pubmed citation
- 2. Cosentino CM, Poulton TB, Esguerra JV et-al. Giant cranial hemangiopericytoma: MR and angiographic findings. AJNR Am J Neuroradiol. 14 (1): 253-6. AJNR Am J Neuroradiol (abstract) - Pubmed citation
- 3. Smith AB, Horkanyne-Szakaly I, Schroeder JW et-al. From the radiologic pathology archives: mass lesions of the dura: beyond meningioma-radiologic-pathologic correlation. Radiographics. 2014;34 (2): 295-312. doi:10.1148/rg.342130075 - Pubmed citation
- 4. Schweizer L, Koelsche C, Sahm F et-al. Meningeal hemangiopericytoma and solitary fibrous tumors carry the NAB2-STAT6 fusion and can be diagnosed by nuclear expression of STAT6 protein. Acta Neuropathol. 2013;125 (5): 651-8. doi:10.1007/s00401-013-1117-6 - Pubmed citation
- 5. Louis DN, Perry A, Reifenberger G et-al. The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. Acta Neuropathol. 2016;131 (6): 803-20. doi:10.1007/s00401-016-1545-1 - Pubmed citation
- 6. Louis DN, Ohgaki H, Wiestler OD, Cavenee WK "WHO Classification of Tumours of the Central Nervous System. 4th Edition Revised" ISBN: 9789283244929
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