Meningeal solitary fibrous tumors (SFTs) and hemangiopericytomas (HPCs) had been combined into a single classification until 2016. Recurrence and metastases rates are still understudied, especially for spinal SFT/HPCs. Here, we describe CNS SFT/HPCs and predictors for recurrence, metastases, and death, in spinal and intracranial SFT/HPCs, separately. We collected data from studies with patient-level data available on primary SFT/HPCs from multiple online databases. Clinico-demographic data, surgical outcomes, recurrence, metastases, and death rates were abstracted. We used logistic and Cox regression models to identify predictors for recurrence, metastases, and death for spinal and intracranial SFT/HPCs. Twenty-nine studies (368 patients) were included. Higher histological grade and subtotal resection were associated with recurrence (p values < 0.05), while higher histological grade and recurrence (p values < 0.005) were associated with metastases formation. Time to recurrence (p < 0.005) and metastases (p < 0.001) formation were shorter for spinal SFT/HPCs. Death rates were higher among intracranial SFT/HPC patients (p value = 0.001). Among patients with higher histological grade, rates of metastases formation were different between intracranial and spinal SFT/HPCs. Risk of metastases was higher in the first 5 years from surgery for both intracranial and spinal SFT/HPCs. Meningeal SFT/HPCs patients have high rates of recurrence and metastasis, which occur mostly within the first 5 years after diagnosis. Spinal and intracranial SFT/HPCs show similar behavior, but spinal SFT/HPCs tend to develop metastases and recurrences in a shorter interval of time. Careful follow-up for spinal SFT/HPCs should be considered because spinal cases seem to be slightly more aggressive and require more attention.

Meningeal solitary fibrous tumor (SFT)/hemangiopericytoma (HPC) is a rare tumor with propensity for recurrence and metastasis. Although multiple classification schemes have been proposed, optimal risk stratification remains unclear, and the prognostic impact of fusion status is uncertain. We compared the 2016 WHO CNS tumor grading scheme (CNS-G), a three-tier system based on histopathologic phenotype and mitotic count, to the 2013 WHO soft-tissue counterpart (ST-G), a two-tier system based on mitotic count alone, in a cohort of 133 patients [59 female, 74 male; mean age 54 years (range 20-87)] with meningeal SFT/HPC. Tumors were pathologically confirmed through review of the first tumor resection (n = 97), local recurrence (n = 35), or distant metastasis (n = 1). A STAT6 immunostain showed nuclear expression in 132 cases. NAB2-STAT6 fusion was detected in 99 of 111 successfully tested tumors (89%) including the single STAT6 immunonegative tumor. Tumors were classified by CNS-G as grade 1 (n = 43), 2 (n = 41), or 3 (n = 49), and by ST-G as SFT (n = 84) or malignant SFT (n = 49). Necrosis was present in 16 cases (12%). On follow-up, 42 patients had at least one subsequent recurrence or metastasis (7 metastasis only, 33 recurrence only, 2 patients had both). Twenty-nine patients died. On univariate analysis, necrosis (p = 0.002), CNS-G (p = 0.01), and ST-G (p = 0.004) were associated with recurrence-free (RFS) but not overall survival (OS). NAB2-STAT6 fusion type was not significantly associated with RFS or OS, but was associated with phenotype. A modified ST-G incorporating necrosis showed higher correlation with RFS (p = 0.0006) and remained significant (p = 0.02) when considering only the primary tumors. From our data, mitotic rate and necrosis appear to stratify this family of tumors most accurately and could be incorporated in a future grading scheme.

In meningiomas, prognostic impact of mutations in the human telomerase reverse transcriptase (hTERT) promoter region was recently shown, while studies of promoter methylation and analyses of hemangiopericytomas are lacking. hTERT promoter methylation was analyzed in 78 meningioma and 38 meningeal hemangiopericytoma samples by methylation-specific polymerase chain reaction (MS-PCR) and compared with histopathological and clinical variables and with immunohistochemical hTERT expression. Promoter methylation was found in 62 samples (53 %) and tended to be higher in meningiomas (N = 19/41, 46 %) than in hemangiopericytomas (N = 8/33, 24 %, p = .057). In meningiomas, methylation was 16, 60 and 77 % in grade I, II and III tumors (p < .001) and higher in recurrent (N = 33/37, 89 %) than in primary diagnosed (N = 19/41, 46 %) tumors (OR 5.14, 95 % CI 1.34-19.71, p = .017). Univariate analyses showed shorter mean progression free and overall survival in methylated than in unmethylated individuals (26 vs. 100 months; p = .045 and 110 vs. 113 months; p = .025, respectively). Moreover, hTERT expression was found in 70 % (N = 53) and was more frequent in methylated than in unmethylated samples (78 vs. 52 %, OR 3.36, 95 % CI 1.20-9.40, p = .021). In hemangiopericytomas, methylation was similar in grade II (24 %) and III (25 %, p > .05) and in primary (24 %) and recurrent tumors (40 %, p > .05). hTERT expression was similar as compared to meningiomas (74 %, N = 28, p > .05) but was independent of promoter methylation (OR 4.26, 95 % CI 0.47-39.0, p = .199). In meningeal tumors, hTERT promoter methylation is more common than mutations and in meningiomas but not in hemangiopericytomas positively correlated with WHO grade and hTERT expression.

Hemangiopericytomas are rare vascular tumors that may be associated with profound hypoglycemia. We present correlative imaging findings for a 57-year-old woman who had multiple abdominal and muscular metastases with severe hypoglycemia 11 years after resection of meningeal hemangiopericytoma. The metastases were well-defined masses containing solid and cystic components, and they were extremely hypervascular in the solid component. Those characteristics on imaging associated with hypoglycemia and the past history of meningeal hemangiopericytoma may suggest the diagnosis and be helpful in differentiating the mass from other vascular tumors. Color and power Doppler ultrasound may play a valuable role in characterizing and diagnosing metastasis from hemangiopericytoma. A delay of several years between diagnosis of the primary hemangiopericytoma and the manifestation of metastasis appears to be a special feature of hemangiopericytoma.

Meningeal solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) are considered to be distinct entities in the WHO Classification of CNS Tumours (2007). They harbor NAB2-STAT6 fusions similar to their soft tissue counterparts, supporting the view that they are part of a tumor continuum. We examined 30 meningeal-based tumors originally diagnosed as either SFT or HPC. These showed a spectrum of morphologic features and were diagnosed as SFTs, malignant SFTs, HPCs, or tumors with \"intermediate\" features. All of the tumors showed nuclear expression of STAT6. SFTs consistently expressed diffuse CD34, while HPCs and intermediate tumors had heterogeneous staining. NAB2-STAT6 fusions were identified in 20 cases, including 7 with exon 4-exon 3, 9 with exon 6-exon 17, and 4 with exon 6-exon 18 fusions. NAB2 exon 4-STAT6 exon 3 fusion correlated with classic SFT morphology and older age and showed a trend toward less mitotic activity; there was also a trend toward more aggressive behavior in tumors lacking NAB2 exon 4-STAT6 exon 3. Thus, despite their clinical and morphologic differences, meningeal-based SFTs, HPCs, and tumors with intermediate features, similar to their soft tissue counterparts, form a histopathologic spectrum unified by STAT6 immunoexpression and NAB2-STAT6 fusion.

OBJECTIVE: Although surgical resection is used to treat meningeal hemangiopericytoma (MHPC), there is a high risk of subsequent recurrence. This study investigated factors associated with treatment outcomes and recurrence in patients who had undergone surgical resection of intracranial MHPC.
METHODS: Fifteen patients underwent surgical treatments performed by one senior neurosurgeon between 1997 and 2013. Clinical data, radiologic images, surgical outcomes, recurrence, and other relevant characteristics were reviewed and analyzed.
RESULTS: Fifteen patients were included in the analysis, 12 (80%) of whom had tumors in the supratentorial region, and 3 (20%) of whom had tumors in the infratentorial region. Complete resection was achieved in all 15 patients, and 3 (20%) patients were administered radiosurgery and conventional radiotherapy after surgery as adjuvant radiotherapy. Three patients developed recurrence, 2 of whom had not received adjuvant radiotherapy. In 1 of the patients who had not received adjuvant radiotherapy, recurrence developed at the original tumor site, 81 months after surgery. The other 2 recurrences occurred at other sites, 78 and 41 months after surgery. The 5- and 10-year overall survival rates were 88.3%, while the 5- and 10-year recurrence-free survival rates were 83% and 52%, respectively. Additionally the mean Ki-67 index differed significantly between patients who did and did not develop recurrence (43% vs. 14%; p=0.001).
CONCLUSIONS: Because of the high risk of MHPC recurrence, MHPC tumors should be completely resected, whenever feasible. However, even when complete resection is achieved, adjuvant radiotherapy might be necessary to prevent recurrence.

Regardless of the controversial pathogenesis, intracranial meningeal hemangiopericytoma (M-HPC) is a rare, highly cellular and vascularized mesenchymal tumor that is characterized by a high tendency for recurrence and extraneural metastasis, despite radical excision and postoperative radiotherapy. M-HPC shares similar clinical manifestations and radiological findings with meningioma, which causes difficulty in differentiation of this entity from those prognostically favorable mimics prior to surgery. Treatment of M-HPC, particularly in metastatic settings, remains a challenge. A case is described of primary M-HPC with recurrence at the initial and distant intracranial sites and extraneural multiple-organ metastases in a 36-year-old female. The metastasis of M-HPC was extremely extensive, and to the best of our knowledge this is the first case of M-HPC with delayed metastasis to the bilateral kidneys. The data suggests that preoperative computed tomography and magnetic resonance imaging could provide certain diagnostic clues and useful information for more optimal treatment planning. The results may imply that novel drugs, such as temozolomide and bevacizumab, as a component of multimodality therapy of M-HPC may deserve further investigation.

OBJECTIVE: Meningeal hemangiopericytoma (HPC) and mesenchymal chondrosarcoma are aggressive neoplasms with a propensity to involve the meninges and dura. In addition to similar clinical presentations, both meningeal HPC and mesenchymal chondrosarcoma share overlapping morphologic features, including ovoid cells, variable collagen deposition, and a branching vascular pattern. Recently, a novel HEY1-NCOA2 fusion was reported as a recurrent event in mesenchymal chondrosarcomas.
METHODS: Thirteen mesenchymal chondrosarcomas and 18 meningeal HPCs were identified from surgical pathology archives, and the tumors were evaluated for HEY1-NCOA2 fusion with reverse transcriptase-polymerase chain reaction (RT-PCR).
RESULTS: HEY1-NCOA2 fusion transcript was detected in all six cases of mesenchymal chondrosarcoma but in none of the meningeal HPC cases (0/11) that were evaluable with RT-PCR.
CONCLUSIONS: These results show that (1) meningeal HPC and mesenchymal chondrosarcoma are distinct at the molecular level, and (2) the identification of HEY1-NCOA2 can be used as an auxiliary diagnostic tool to differentiate these entities.