meningeales Hämangioperizytom

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.

Epidemiology

Hemangiopericytomas account for less than 1% of all intracranial tumors . They are typically encountered in younger adults (30-50 years) with up to 10% being diagnosed in children . There is a slight male predilection (M: F 1.4:1) .

Clinical presentation

Clinical presentation is usually due to mass effect and will vary depending on location. Headache, seizures, focal neurological dysfunction may all be presenting features . Additionally, in up to 20% of cases, these tumors can metastasize systemically, typically to liver, lung, and bone .

Pathology

Hemangiopericytomas were previously classified as angioblastic sub-type meningiomas, then considered to arise from smooth muscle perivascular pericytes of dural capillaries (pericytes of Zimmerman) ,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 . 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 . In fact, in the 2016 update to the WHO classification of CNS tumors, the two entities have been combined .

Solitary fibrous tumors of the dura are WHO I grade one lesion, whereas hemangiopericytomas are WHO grade II or III (anaplastic) tumors .

Microscopic appearance

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 .  The cells are separated by a limited amount of delicate reticulin fibers and have numerous "staghorn" vessels, the latter a feature shared by solitary fibrous tumors of the dura .

Immunophenotype

Ideally, the diagnosis is confirmed by assessing for STAT6 expression by immunohistochemistry or identifying NAB2-STAT6 fusion . Hemangiopericytomas have a number of useful immunohistochemical markers :

• STAT6: positive
• CD34: positive
• vimentin: positive

Ki-67 proliferation index is typically around 10% .

Radiographic features

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

Another common location is the posterior fossa in the posterior occipital region.

CT

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

MRI

Features on various sequences include

• 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 tumors
• ​T2
  • 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
  • high myoinositol
  • absent alanine peak (present in meningiomas)
• DWI
  • intermediate restricted diffusion (less than meningioma) 
  • minimum ADC ~ 1100 (+/- 130) x 10 mm/s 

Angiography

• ECA, ICA and vertebral supply common
• highly vascular
• corkscrew arteries
• fluffy tumor stain
• lack of early draining veins
• 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 . Adjuvant radiotherapy to reduce the incidence of recurrence has also been advocated .

Differential diagnosis

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.

• 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
  • 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

Siehe auch:

• Meningeom
• meningeale Kontrastmittelaufnahme
• Hämangioperizytom
• meningeale Tumoren
• meningeale Neoplasien
• haemangiopericytoma (CNS)

und weiter:

• intrakranielles Hämangioperizytom