General
- AKA: (both not used anymore)
- Haemangiopericytoma
- Angioblastic meningioma
Features | Haemangiopericytoma | SFTs |
ㅤ | Oval to round cells | More spindle-cell morphology with thick collagen bundles |
- Use to be two different tumours that has now been grouped into one due to their molecular similarity
- SFT is considered a sarcoma; therefore, it should be treated as such.
Definition
- Essential:
- Variably cellular tumour composed of spindled to ovoid cells arranged around a branching and hyalinized vasculature AND
- Variable stromal collagen deposition AND
- STAT6 nuclear expression
- Desirable (in selected cases):
- Demonstration of NAB2::STAT6 gene fusion
Numbers
- True incidence and prevalence of this entity are difficult to ascertain, due to inconsistent nomenclature.
- < 1% of all primary CNS tumours
- Commonly in 40-60yr old
- Average annual age-adjusted incidence rate of 0.08 cases per 100 000 population
- Males slightly > females
- Paeds exceedingly rare
Grading
- Grading is based on a combination of mitotic activity and the presence of necrosis.
WHO grade | Mitoses/mm2 | Mitoses/10 HPF | Necrosis presence |
1 | < 2.5 | < 5 | n/a |
2 | > 2.5 | > 5 | No |
3 | > 2.5 | > 5 | Yes |
Origin
- Smooth muscle pericytes around the capillaries of the meninges
- But it is felt both came from the same cell of origin because of the similar NAB2-STAT6 fusion
Histopathology
Macroscopic features
- Tumours are typically dural-based, well-circumscribed, and firm.
- The colour of the mass ranges from white to reddish-brown depending on the degree of collagenous stroma and cellularity.
Microscopic features
- The tumour typically exhibits a patternless architecture of monomorphic spindle cells admixed with hyalinised, thin-walled, branching staghorn-shaped vessels.
- The spectrum ranges from paucicellular tumours with abundant keloidal-type collagen to highly cellular tumours with minimal stroma.
- Reticulin fibres are often abundant and highlighted by silver staining.
Grade 1
- More fibrous
- Pattern less architecture or short fascicular pattern, with alternating hypocellular and hypercellular areas with thick bands of collagen
- Thin-walled branching hemangiopericytoma-like (staghorn) vessels are a feature shared by both phenotypes.
Image
Grade 2 & 3
- More cellular
- Histopathology high cellularity and a delicate, rich network of reticulin fibres typically investing individual cells.
Image
Immunophenotype
- Positive
- Intense and diffuse nuclear expression of STAT6 is the hallmark diagnostic feature.
- Diffusely vimentin and CD34
- Loss of CD34 is common in malignant tumours
- Reticulin
- Vimentin
- Von Willebrand factor (perivascular spaces)
- ALDH1 is a robust and specific marker for this tumour type.
- Negative
- Epithelial membrane antigen
- S100 protein.
Genetic
- No evidence of familial clustering of meningeal solitary fibrous tumour / haemangiopericytoma.
- A genomic inversion at the 12q13 locus → fusing the NAB2 and STAT6 genes →
- This gene fusion is present in most cases, regardless of histological grade or anatomical location (meningeal, pleural, or soft tissue).
- Only extracranial rare sinonasal haemangiopericytoma does not exhibit the NAB2STAT6 fusion, but instead harbours CTNNB1 mutations
- STAT6 protein
- Normal function
- Induce the expression of BCL2 → anti-apoptotic activity
- NAB2
- Normal function
- Repress or activate transcription induced by some members of the EGR (early growth response) family of transactivators.
- NAB2-STAT6 fusion leads to nuclear relocalisation of STAT6 protein and can be detected: shows nuclear staining for STAT6
- Specific fusion variants correlate with tumour grade, as fusions involving NAB2 exon 4 and STAT6 exon 2 or 3 are typically seen in hypocellular grade 1 tumours.
- TERT promoter mutations are identified in 10 to 30 percent of meningeal cases.
Localisation
- Mainly supratentorial: arise from dura
- Common
- Skull base
- Parasagittal
- Falcine
- Uncommon locations
- CP angle
- Pineal gland
- Sellar region
- 10% spinal: arise directly from cord
Clinical features
- Due to
- Mass effect, with increased intracranial pressure due to tumour size
- Rare:
- Massive intracranial haemorrhage
- Hypoglycaemia from tumours that release insulin-like growth factor are rare complications.
Radiological features
- CT
- Well circumscribed and isodense to hyperdense
- Vivid enhancement
- May demonstrate calcifications,
- No hyperostosis or calcification
- May erode bone if abutting it
- CT+C
- T1
- Isointense
- T1+C
- Vivid diffuse heterogeneous contrast enhancement of low T2 signal components
- May have a narrow base of dural attachment, dural tail sign is seen, more commonly in grade II tumour
- Dural tail may be seen, but is much less common than in meningiomas
- T2
- iso- to hypointensity
- Heterogeneous signal: "yin-yang" appearance of separate areas with low signal and high signal intensity may be characteristic
- Adjacent brain oedema frequently present
- Multiple flow voids on MRI (need to distinguish from the spoke-wheel appearance of meningioma)
- MRS
- myo-inositol elevation
- Lipid and lactate elevation
- Absent alanine peak (present in meningiomas)
- Flair
- DWI
- ADC
Treatment
- Surgery
- Surgical resection is the primary management strategy.
- GTR has better outcome
- Adjuvant treatment
- Hemangiopericytoma is considered a sarcoma; therefore, it should be treated as such.
- Radiotherapy or radiosurgery is often utilised for the management of residual or recurrent disease.
- However, the often dramatic radiographic regression with radiation continues to support its use both in primary and recurrent disease.
- It can be administered either in the form of fractionated radiotherapy or stereotactic radiosurgery.
- Chemotherapy, on the other hand is usually administered as a salvage treatment.
- Most commonly used agents include doxorubicin, ifosfamide, etoposide, methotrexate, cyclophosphamide, cisplatin, mitomycin, and vincristine.
Prognosis
- SFT has a high propensity for recurrence and metastasis
- Can occur decades after the initial diagnosis
- In a cohort of 132pt
- Recurrent disease occurred in 40% after a median of 36 months
- 10% (of total) recurred after 10 years
- 12% patients died of the disease after a median period of 70 months
- Recurrence often occurs in even grade 1 → need routine post op radiological f/u
- Not prognostic
- Size of tumour
- Age
- Presence of NAB2:STAT6 fusion
- Prognostic
- Grade (Ki67 & Necrosis)
- Low grade
- Benign if
- Gross total resection can be achieved and
- No atypical histological features
- Prognostic significance of focal (rather than generalized) atypia in these tumours and of invasion in bone and dural sinuses is unclear
- High grade
- In a recent surgical series, 5-year survival and disease-free survival rates are reported as 93% and 89%, respectively.
- High rate of recurrence (> 75% in patients followed for > 10 years) even after gross total resection.
- 20% of patients develop extracranial metastases (bone, lung, and liver)
- Gross total resection favourably affects recurrence and survival, and patients benefit from adjuvant radiotherapy
- Grade of surgical resection
Differential diagnosis
Meningothelial and soft tissue neoplasms
Fibrous meningioma | Solitary fibrous tumour | |
+ | Desmin, SMA, cytokeratin, EMA, and progesterone receptor, ALDH1A1 gene overexpression (by microarray analysis) 84% | CD34, Nuclear STAT 6, ALDH1A1 gene overexpression (by microarray analysis) 1% |
- | CD34 Nuclear STAT 6 (meningiomas show faint + for stat6 in both nucleus and cytoplasm) | Desmin, SMA, cytokeratin, EMA, and progesterone receptor |
Feature | Meningioma | Sarcoma | Hemangiopericytoma |
Location | Supratentorial > infratentorial > spine | Supratentorial = infratentorial | Supratentorial > infratentorial > spine |
Incidence | 15%-20% of intracranial tumors | Less than 1% of intracranial tumors | 1% of intracranial tumors |
Age | 5th decade | Highly variable | 4th decade |
Sex | Female > male | Male = female | Male > female |
Recurrence | Infrequent | Expected | Expected |
Metastatic potential outside CNS | Minimal | High | High |
Imaging | CT/MRI | CT/MRI | CT/MRI |
Enhancement | Homogeneous enhancement | Typically homogeneous, although necrotic areas and heterogeneity are not uncommon | Typically homogeneous, although necrotic areas and heterogeneity are not uncommon |
Calcification | Common | Rarely | Rarely |
Effect on bone | Hyperostosis | Bone erosion | Bone erosion |
Primary treatment | Surgery—goal of total resection | Surgery—goal of total resection | Surgery—goal of total resection |
Preoperative embolization | Rare except for skull base lesions | Based on location | Probably beneficial regardless of location |
Radiotherapy/radiosurgery | Rarely necessary unless high grade or inoperable | Unclear with total resection, clearly indicated with subtotal disease or with recurrence | Unclear with total resection, clearly indicated with subtotal disease or with recurrence |
Dural-based Ewing sarcoma / peripheral primitive neuroectodermal tumour
Dural-based Ewing sarcoma / peripheral primitive neuroectodermal tumour | Haemangiopericytoma | |
Difference | No STAT6 staining Presence of EWSR1 gene rearrangement | Has STAT 6staining |
Similarity | hypercellularity and CD99 positivity | hypercellularity and CD99 positivity |
Primary and metastatic monophasic synovial sarcomas
Primary and metastatic monophasic synovial sarcomas | Solitary fibrous tumour / haemangiopericytoma |
Immunoreactivity for EMA and TLE1 and/or FISH analysis for the presence of SS18 gene rearrangement |
Mesenchymal chondrosarcoma, a rare malignant tumour
- With a bimorphic pattern, is composed of sheets and nests of poorly differentiated small round cells interrupted by islands of well-differentiated hyaline cartilage and a branching vasculature.
- Because the cartilage islands can be extremely focal, this entity may be mistaken for malignant solitary fibrous tumour / haemangiopericytoma if insufficiently sampled
Malignant peripheral nerve sheath tumour | Haemangiopericytoma |
Both has similar microscopic findings | |
Rare in meninges | Mainly in meninges |
Negative for CD34 and STAT6 | Positive for CD34 and STAT6 |
Positive for S100 and SOX10 | Negative for S100 and SOX10 |
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