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NI FEATURE: PATHOLOGICAL PANORAMA - ORIGINAL ARTICLE
Year : 2018  |  Volume : 66  |  Issue : 5  |  Page : 1419-1426

Meningeal solitary fibrous tumor/hemangiopericytoma: Emphasizing on STAT 6 immunohistochemistry with a review of literature


Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Karachi, Pakistan

Date of Web Publication17-Sep-2018

Correspondence Address:
Dr. Nasir Ud Din
Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Karachi
Pakistan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.241365

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 » Abstract 


Background: The 2016 central nervous system (CNS) World Health Organisation (WHO) Update has merged the entities of meningeal solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) into a single entity based on the presence of the nerve growth factor 1A (NGFI-A) binding protein 2 (NAB2)- signal transducer and activator of transcription 6 (STAT6) gene fusion in these tumors. Immunohistochemical (IHC) staining with STAT6 results in a strong nuclear positivity confirming the diagnosis. Meningeal SFT/HPCs are currently histologically graded according to a three-tiered system. Grade I (SFT phenotype) is benign, whereas grades II and III (HPC phenotype) are malignant and require radiotherapy in addition to gross total resection.
Objectives: The objectives were to review the cases diagnosed as meningeal SFT or HPC between 2010 and 2017 and classify them into SFT (grade I) or HPC (grades II and III) phenotypes; to confirm the diagnosis by performing STAT6 immunohistochemistry; and to observe and record the histological features in detail and correlate the tumor grades with their behavior. The published literature on the subject was also reviewed.
Materials and Methods: A total of 21 cases diagnosed between 2010 and 2017 as meningeal SFT or HPC were included in the study. All cases were reviewed by the authors and were categorized and graded according to histologic phenotype and mitotic count. STAT6 immunohistochemistry was performed in all the cases. The epidemiological data and histologic findings in each case were recorded in detail. The follow-up of patients was obtained.
Results: Fifteen patients were males and six were females. The mean age was 43.5 years. The mean tumor size was 6.8 cm. The tumor specimens in 20 out of 21 cases corresponded to the HPC phenotype, of which 6 were in grade II while 14 were in grade III. Thus, over 95% cases had malignant lesions. The tumor in all the 21 cases recruited for the study showed immunohistochemical positivity for SAT6, while CD34 was positive in all the 18 tumor in which it was performed. The follow-up was available in 14 of the patients. Recurrence occurred in six patients who had either a grade II or a grade III tumor and three patients died (including one patient with a grade III tumor. This patient died a month after initial resection although there was no evidence of recurrence). Radiotherapy was given to only 4 out of 14 patients in whom follow-up was available.
Conclusion: These rare tumors need to be accurately diagnosed and optimally treated (gross total resection and radiotherapy) to improve the prognosis.


Keywords: Hemangiopericytoma, meningeal, solitary fibrous tumor, STAT6
Key Message: Meningeal solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) have been clubbed into a single entity based on the presence of the nerve growth factor 1A (NGFI-A) binding protein 2 (NAB2)- signal transducer and activator of transcription 6 (STAT6) gene fusion in these tumors. In the present study, the majority of tumors of the SFT-HPC grouping showing evidence of this gene fusion had an extremely diverse location, and 95% of them were malignant, belonging to the HPC variety. Total excision is recommended to improve their prognosis. Adjuvant radiotherapy is reserved for the malignant cases. A review of literature conducted in this study correlates the histological and immunohistochemical associations of these tumors. Lack of awareness regarding this entity may often lead to its misdiagnosis.


How to cite this article:
Ahmad Z, Tariq MU, Din NU. Meningeal solitary fibrous tumor/hemangiopericytoma: Emphasizing on STAT 6 immunohistochemistry with a review of literature. Neurol India 2018;66:1419-26

How to cite this URL:
Ahmad Z, Tariq MU, Din NU. Meningeal solitary fibrous tumor/hemangiopericytoma: Emphasizing on STAT 6 immunohistochemistry with a review of literature. Neurol India [serial online] 2018 [cited 2018 Oct 23];66:1419-26. Available from: http://www.neurologyindia.com/text.asp?2018/66/5/1419/241365




For a very long time since they were first recognized, solitary fibrous tumors (SFTs) and hemangiopericytomas (HPCs), whether arising in the soft tissue or in the central nervous system (CNS), that is, in the meninges, were considered as separate tumor entities.[1] However, since the early 1990s, as increasing evidence suggesting a close relationship between the two tumor entities began to accumulate, the pathologists, at least in soft tissues, began to consider SFTs and HPCs as a single entity.[2],[3],[4],[5] This view was cemented by the discovery of a common oncogenic event, that is, NAB2-STAT6 gene fusion in both the tumors in 2013;[6],[7],[8],[9] and, the 2013 World Health Organization (WHO) Classification of Tumors of Soft tissue and Bone merged the two entities, placing all such tumors in the category of extrapleural SFTs. At the same time, the term ‘hemangiopericytoma' started being considered as obsolete.[10],[11] The 2007 WHO CNS classification listed the meningeal SFTs and HPCs separately,[12] but the 2016 revised 4th edition (2016 update) has merged the two, based on the presence of the NAB2-STAT6 gene fusion in the meningeal SFTs and HPCs. However, unlike the situation in the soft tissues, the WHO has not considered the term ‘hemangiopericytoma' as being obsolete and has retained the rather ungainly name “solitary fibrous tumor/hemangiopericytoma” for these tumors, as the histogenesis of these CNS tumors still remains a matter of debate.[13] Like their soft tissue counterparts, most meningeal SFTs/HPCs demonstrate a genomic inversion at the 12q13 locus that leads to the fusion of the NAB2 and STAT 6 genes. This in turn results in nuclear localization and expression of STAT6 by the tumor cells that can be detected by immunohistochemistry (IHC) due to the strong nuclear positivity.[8],[9],[14] The 2016 CNS WHO classification highly recommends either molecular or IHC testing for the NAB2-STAT6 fusion and the STAT6 nuclear expression, respectively, for confirming the diagnosis of these tumors, and emphasizes that a negative result should lead to consideration of an alternative diagnosis. It also states that if and when the above tests are not available or cannot be performed, the fact should be clearly mentioned in the report.[13]

Meningeal SFT/HPCs are divided into three histological grades: Grade I (SFT histologic phenotype) tumors are considered benign and are treated by surgical resection alone; whereas, grades II and III (HPC histologic phenotype) tumors are considered malignant and the patients also receive adjuvant radiotherapy. [10, 12, 13, 15-17]

We retrieved 21 cases diagnosed as meningeal solitary fibrous tumors or hemangiopericytomas since 2010 from our files. The purpose was twofold: One was to grade these tumors based on the SFT or HPC histology and mitotic count and describe the histologic features in detail; and, the other was to perform the STAT6 IHC on all cases to confirm the diagnosis. We also present a detailed review of the recent literature on CNS SFT/HPCs.


 » Materials and Methods Top


A total of 21 cases diagnosed either as meningeal solitary fibrous tumor or hemangiopericytoma between 2010 and 2016 were retrieved from the surgical pathology files of the Section of Histopathology, Department of Pathology, and Laboratory Medicine. The hematoxylin and eosin (H and E) and IHC slides of all 21 cases were reviewed by the authors. The cases were categorized and graded according to the histologic phenotypes and mitotic count (if they were histologically corresponding to the HPC phenotype). A STAT 6 immunohistochemical staining was performed on the representative paraffin blocks of all 21 cases and the STAT6 stained slides were reviewed by the authors. Follow-up was sought and obtained in 14 out of 21 patients. The remaining 7 patients were lost to follow up. The clinical and morphological data (age, gender, exact location, tumor size, etc.) were obtained from the surgical pathology reports. Patients were contacted on the telephone numbers provided at the time of specimen submission. Verbal consent and follow-up information were obtained from the patients or relatives (in case of patients who had died).

Various immunohistochemical stains performed in the above cases included: Vimentin (Vim 3B4, 1:10;Dako), CKAE1/AE3 (cytokeratin clone AE1/AE3,1:50; Dako), EMA (epithelial membrane antigen, E29,1:50; Dako), CD34 (cluster of differentiation; 1:400; Dako), S100 (1:1000; Dako, Carpinteria, CA), CD99 (Mic 2, 1:50), GFAP (Glial fibrillary acidic protein, 1:200), CD31 (1:50), ASMA (anti smooth muscle actin, D33, 1:150; Dako), desmin (D33, 1:150; Dako), BCL2 (B-cell lymphoma 2; 1:100), and STAT6 (Santa Cruz, 1:200).


 » Results Top


Out of 21 patients in our study, 15 (71.4%) were males and 6 (28.6%) were females. The male-to-female ratio was 2.5:1. The mean and median age of the patient cohort was 43.5 and 45 years, respectively. Their age range was from 18 to 65 years. Our cases showed a wide variation in the location of tumor [Figure 1]a-d] and the tumor size. The breakup of tumor characteristics is shown in [Table 1]. In 6 cases, the exact location was not known. Of the remaining 15 cases, at least 5 (31.2%) were located in uncommon locations [Table 1]. The tumor size ranged from 3.5 cm to 16.5 cm. The mean tumor size was 6.8 cm. In all the 21 cases, the tumor was removed in multiple pieces. The age and gender of the patients and the site and size of the tumor are shown in [Table 1]. Of the 21 cases, only 1 (4.8%) tumor sample corresponded histologically to the SFT phenotype (grade I) [Figure 2]a and b]. All the remaining 20 tumors corresponded histologically to the HPC phenotype [Figure 3]a and b]. Of the latter group, 6 (28.6%) tumors were in grade II and 14 (66.7%) were grade III [Figure 4]a and b]. Thus, over 95% cases in this study were malignant. The single case with the SFT histological phenotype showed a mild cellularity, whereas the 20 cases with HPC phenotype showed a moderate (11; 52.4%)-to-marked (9; 42.8%) cellularity. Six grade II tumors were moderately cellular. Of the 14 grade III tumors, 9 (64.3%) were markedly cellular whereas 5 (35.7%) were moderately cellular. The detailed histological characteristics are shown in [Table 2] [Figure 2]c and d]. CD34 was performed in 18 cases and was positive in all of them [Figure 3]c. All 21 cases showed nuclear positivity for the IHC stain STAT6 [Figure 3]d. The follow-up was available in 14 out of 21 cases. It was available in the single grade I tumor in our study, in 5 out of the 6 grade II tumors (83.3%), and in 8 out of the 14 grade III tumors (57.1%). The single patient with grade I tumor underwent resection in 2014. No further treatment was given and the patient has been alive and well with no recurrence or metastasis. Two out of the five patients with grade II tumors (in whom follow-up was available) underwent resection in 2010 and 2011, respectively. No additional treatment (radiation) was given. The former developed recurrence in 2016, six-and-a-half years after the initial resection, and underwent a second resection the same year (2016). He received adjuvant radiation therapy after developing recurrence and has had an overall survival (OS) time of 87 months at the time of follow-up. The second patient developed a recurrence in 2016 (just over 5 years after the initial resection). She underwent another resection but died a month later. No radiation therapy was given. The third patient with a grade II tumor underwent resection in 2014. He received adjuvant radiotherapy and had been alive and well without a recurrence or metastasis at the time of follow-up (38 months after resection). The fourth patient with a grade II tumor underwent resection in late 2016 but did not receive any adjuvant therapy. He was alive and well at the time of follow up, six months after resection of the tumor, with no evidence of recurrence or metastasis. The fifth patient with grade II tumor was diagnosed in the early 2017 and underwent resection only one-and-a-half months ago. He has not so far received any radiation therapy and is alive and well one month after surgery with no evidence of recurrence or metastasis. Of the eight patients with grade III tumors (with whom follow-up was available), one died only a month after undergoing surgery. No radiation therapy was given. Two patients with grade III tumors underwent tumor resection in 2012 and 2013, respectively. The former developed a recurrence three-and-a-half years after the initial resection of the tumor and underwent a second surgery in late 2015. He did not receive radiation treatment either in 2012 or 2015 and was alive at the time of follow-up of 59 months. The latter developed a recurrence two-and-a-half years following tumor resection but did not undergo a repeat surgery and did not receive any adjuvant radiotherapy. He died four months after developing recurrence. Another patient with grade III tumor underwent its resection in 2014 but did not receive adjuvant therapy. He developed a recurrence 3 years after the initial tumor resection but was subsequently lost to follow-up. Another patient with a grade III tumor underwent tumor resection in 2016 and received radiotherapy. He was alive and well 11 months after the resection with no evidence of recurrence or metastasis. The 3 remaining patients with grade III tumors, in whom follow-up was available, underwent surgical resection of the tumor in 2013, 2015, and 2017, respectively. Of these, the first patient developed a recurrence in 2016, 38 months after the initial resection. He underwent a second resection in 2016 and also received adjuvant radiotherapy. The patient who underwent surgical resection in 2015 is alive and well two years after the diagnosis, with no evidence of recurrence or metastasis. He received chemotherapy as well as radiotherapy. The last patient with a grade III tumor, in whom follow-up was available, underwent a surgical resection of his tumor 3 months ago. He has not received any adjuvant radiotherapy and has no evidence of recurrence or metastasis so far [Table 3].
Figure 1: (a) T1 sagittal post-contrast image showing a midline mass, arising from the falx, growing posteriorly and producing a mass effect over the frontal lobes. (b) T1 axial post-contrast image showing an enhancing, lobulated, dumbbell-shaped lesion, growing towards both sides and producing a mass effect over both the frontal lobes. (c) T2 sagittal image showing an isointense lesion, producing mass effect and resulting in edema in the underlying frontal lobes. (d) Large dumbbell-shaped, extra-axial mass lesion isointense on T2 weighted image. Significant edema is identified in the adjacent frontal lobes, secondary to mass effect

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Table 1: Summary of clinicopathological features (n=21)

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Figure 2: (a and b) Solitary fibrous tumor phenotype. Bland ovoid-to-spindle cells deposited in a hyaline collagen (haematoxylin (H) and eosin (E), 100× magnification). (c) Nuclear palisading was seen in a single case, which is a rare finding (H and E, ×200 magnification). (d) Cystic spaces reminiscent of glands lined by similar tumor cells were also seen in a single case (H and E, ×200 magnification)

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Figure 3: Hemangiopericytoma phenotype, grade II. (a) Tumor cells arranged in fascicles with thin branching vessels (H and E, ×200 magnification). (b) Storiform pattern of growth (H and E, ×200 magnification). The tumor cells are positive for CD34 (c) and STAT6 (d) immunohistochemical stains

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Figure 4: Hemangiopericytoma phenotype, grade III (a and b). A cellular tumor with round-to -oval hyperchromatic nuclei, increased mitosis, and focal necrosis (H and E, 100 and ×200 magnification)

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Table 2: Summary of histological features (n=21)

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{Figure 2}
Table 3: Summary of follow up of patients (n=14)

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 » Discussion Top


The 2016 CNS WHO update divides meningeal SFT/HPCs into two categories: (i) the solitary fibrous tumor histopathological phenotype that is characterized by a pattern-less architecture. The tumor is a hypocellular and collagenized tumor, composed of bland ovoid-to-spindle shaped cells. There is stromal and perivascular hyaline collagen deposition. This phenotype corresponds to histologic grade I, is considered benign, and is typically treated by surgical resection alone with no adjuvant therapy; and, (ii) the hemangiopericytoma histopathological phenotype that is a densely cellular tumor characterized by a diffuse and a high cellularity. It is composed of closely apposed tumor cells with round-to-ovoid nuclei arranged haphazardly with little intervening stroma. Thin walled, branching blood vessels can be seen. The tumors with the HPC phenotype correspond to the histologic grade II if the mitotic count is <5/10 high power fields (HPF), and to the grade III (or anaplastic) if the mitotic figures are >5/10HPF. The grade II and III tumors (HPC phenotype) are considered malignant, and in addition to surgical resection, patients benefit from adjuvant radiotherapy. [13,15–17] In our study of 21 cases, only 1 (4.8%) corresponded to the SFT phenotype (grade I), whereas 20 (95.2%) corresponded histologically to the HPC phenotype (grades II and III). Out of these 20 tumors with the HPC phenotype (grades II and III), 6 (28.6%) showed <5 mitosis per 10HPF and were categorized as grade II, whereas 14 (66.6%) showed >5 mitosis per 10HPFs and were categorized as grade III. Focal-to-extensive necrosis was seen in three cases (14.3%). All these cases were histologically grade III. Although studies have looked at the possibility of introducing a newer three- or four-tiered grading systems, based on factors such as the mitotic count, hypercellularity, necrosis, etc., the 2016 CNS WHO classification believes that it is not feasible currently to replace the existing grading system described above because studies proposing other systems have also reported that mitotic count remains the only independent prognostic factor determining progression-free survival (PFS) and overall survival (OS) in these tumors.[4] Thus, the three-tiered histological grading system is currently recommended. A very recent study by Zeng et al.,[18] also utilized this “Marseille grading” to analyze 58 cases of intracranial SFT/HPC. They found that the 3-tiered grading reflected a malignant progression ranging from conventional SFTs (grade I) to HPCs (grades II and III), and that the histologic grade negatively correlated with the progression-free and overall survival of these tumors. They also found that gross total resection significantly and positively correlated with the progression-free survival (PFS) and overall survival (OS) of these tumors. They also found significant positive correlation of radiotherapy with PFS and OS in tumors with the HPC phenotype. Both Bouvier et al.,[4] and Zeng et al.,[18] agreed that the overlapping pathological features and common prognostic markers favored the unification of meningeal SFTs and HPCs into a single entity.

Historically, numerous studies that compared the biological behavior of meningeal SFTs and HPCs as separate entities noted that the tumors that corresponded histologically to SFTs were characterized by slow growth, low local recurrence rates, and almost never metastasized outside the CNS. On the other hand, tumors that corresponded histologically to HPCs were characterized by rapid growth, high local recurrence rates, and often metastasized outside the CNS. This was true even for those meningeal HPCs that did not demonstrate a high mitotic rate or necrosis. Studies have shown that gross total resection is important for tumors with either the SFT or HPC histology, and for the latter, adjuvant radiotherapy significantly minimizes the risk of recurrence, provided gross total resection has been achieved.[5],[19]

Since the entities previously listed separately as SFT or HPC overlap considerably in their clinical, radiological, immunohistochemical, and ultrastructural features, a debate on whether or not these two lesions could represent a single tumor entity, went on for years. However, the opinion began to shift in favor of SFT and HPC being a single entity, at least in the extrapleural soft tissues, with the demonstration of the common NAB2-STAT6 gene fusion in both these tumors in 2013.[2], 3, [20],[21],[22],[23],[24],[25],[26],[27],[28] The Soft Tissue WHO Committee dropped the term “hemangiopericytoma” and incorporated all these tumors into the common category of extrapleural SFTs.[10],[11] As newer studies began to conclusively demonstrate the presence of the same genetic fusion in both meningeal SFTs and HPCs, which served as a strong evidence for a morphologic continuum of the two entities, the 2016 CNS WHO also merged the two entities as one. However, it retained the term “hemangiopericytoma” and these tumors are now incorporated as a single entity termed “solitary fibrous tumor/hemangiopericytoma.”[13] The presence of NAB2-STAT6 fusion that results in a strong nuclear signal in STAT6 immunohistochemistry was first reported in meningeal SFTs and HPCs by Schweizer et al.,[6] Doyle et al.,[7] and Nakada et al.,[29] and they agreed that not only did this support the unification of these meningeal tumors into a single entity (as has already been done in the case of soft tissue tumors) but that the immunohistochemical stain could practically help and, in fact, prove valuable in differentiating these meningeal tumors from histological mimics. Recently, Savary et al.,[30] noted that the almost constant immunohistochemical expression of STAT6 by both meningeal HPCs and SFTs justified their classification as a single entity and recommend a long-term follow-up due to a high rate of local recurrence in the tumors with a HPC histologic phenotype. More recent studies by several authors, including Fritchie et al.,[31] Zhang et al.,[32] Yuzawa et al.,[33] and Berghoff et al.,[34] have also shown that in spite of clinicopathological differences, meningeal SFTs and HPCs, similar to their soft tissue counterparts, form a histologic spectrum unified by the NAB2-STAT6 fusion and STAT6 expression, as detectable by IHC. It was also stated that the STAT6 immunohistochemistry is a relatively specific marker and a robust method for diagnosing meningeal SFT/HPCs and for differentiating these tumors from other meningeal tumors. Berghoff et al.,[34] recommended including STAT6 IHC in the diagnostic workup of all meningeal tumors as well as soft tissue SFTs. Aldehyde dehydrogenase 1 (ALDH1) is another marker that has been demonstrated to be useful in differentiating these tumors from a meningioma. Studies have shown it to be a sensitive and specific marker for SFT/HPCs.[35],[36],[37]

Recently, other investigators have shown that the NAB2-STAT6 fusions have highly heterogeneous exon compositions such as NAB2 ex6-STAT6 ex-17, NAB2 ex2-STAT6 ex2, NAB2ex4-STAT6ex4, etc.[38] According to some authors such as Tai et al.,[39] these NAB2-STAT6 fusion variants are associated with several clinicopathological factors and, therefore, their prognostic relevance needs to be validated in large prospective studies. This view is shared by Nakada et al.,[40] who recently concluded that clinicopathological data, including yearly follow-ups, are required in meningeal SFT/HPCs to define the correlation of variants of NAB2-STAT6 fusion gene. However, Huang et al.,[41] believe that clinical aggressiveness in meningeal SFT/HPC is not related to the NAB2-STAT6 fusion variants and is primarily associated with the presence of an atypical/malignant histology and increased mitotic activity. According to Kao et al.,[38] the meningeal SFTs/HPCs demonstrate considerable heterogeneity with regard to their exact location, histological patterns, and NAB2-STAT6 fusion variants. Two recent articles by Berghoff et al.,[34] and Zeng et al.,[18] show that STAT6 expression by IHC is a robust method for the diagnosis of meningeal SFT/HPC and should be a part of the diagnostic workup of meningeal tumors, whereas gross total resection and radiotherapy show significant positive correlation with survival in these tumors. Zeng et al.,[18] also agreed that the histological grading of these tumors supports their unification into a single tumor entity.

The STAT6 immunohistochemical stain was positive in all the 21 patients of our study, confirming our diagnosis. We acquired and validated the antibody in the second half of 2016. The tests were performed prospectively in 4 out of 21 cases. These results were reported in the late 2016 and early 2017. In the remaining 17 cases that had been reported before the antibody was acquired, STAT6 was performed retrospectively on the blocks retrieved from our files. IHC stain CD34 was performed in 18 of 21 cases and was positive in all. Meningeal SFT/HPCs typically show diffuse positivity for CD34 and vimentin, whereas STAT6 is highly sensitive (96%) and specific (100%). CD34 and ALDH1 also demonstrate excellent sensitivity (>80%) and specificity (>95%) in meningeal SFT/HPCs.[35],[36] We do not currently have the ALDH1 immunostain. We usually use a panel of the following IHC stains to differentiate between meningeal SFT/HPCs and meningiomas: STAT6, CD34, EMA, and S100 protein.

Out of 21 patients in our series, 15 (71.4%) were males and 6 (28.6%) were females. Their mean and median ages were 43.5 and 45 years, respectively. The age of the patients ranged from 18 to 65 years. According to the published data, the peak incidence of the tumors is in the fourth to fifth decades of life, which supports our results. However, males were much more commonly affected in our series, whereas the published literature supports a slight female predominance.[17],[42],[43] Location wise, our cases demonstrated a wide variation [Table 1]. None of our cases had a spinal origin, although the specific site of the tumor was not known in 6 out of 21 cases. According to the published data, the common locations for these tumors include the skull base, falx cerebri, and parasagittal region, whereas uncommonly, these tumors are located at the cerebellopontine angle (CPA), in the pineal gland and the sellar region. As shown in [Table 1], out of 18 cases in our study (in which the tumor location was known), at least 5 (31.2%) were located in uncommon locations such as the CPA, posterior fossa, occipital lobe and the sellar region.[17],[42],[44],[45]

Histologically, only a single case out of the 21 cases reported, corresponded histologically to the SFT phenotype (grade I), whereas all the remaining 20 cases corresponded to the HPC phenotype (grade II and III) and were malignant. The only patient with the benign SFT phenotype (grade I) underwent resection of his tumor in 2014, did not receive adjuvant radiotherapy, and was alive and well without any recurrence three years after surgery. However, a look at the results [Table 1] shows that the majority of patients in our study with grade II or III tumors developed recurrence and three patients (2 with grade II and 1 with grade III tumor) died of their disease. One of these patients with a grade III tumor died within a month after resection. Thus, the majority of grade II and grade III tumors behaved in a malignant fashion.

There may be lack of optimal facilities for performing surgery and/or radiotherapy. In a number of cases, gross total resection of CNS tumors may not be achieved, thus worsening the prognosis. Many neurosurgeons and oncologists are not familiar with rare CNS tumors, such as SFTs/HPCs. All these factors may lead to a recurrence of the tumor or its inadequate management. According to a study carried out in our section to determine the frequency of CNS neoplasms in our practice, meningiomas comprised 134 (22%) of a total number of 597 cases of CNS tumors reported that year.[46] In comparison, not a single case of meningeal SFT/HPC was reported and, as shown in the current study, only 21 cases have been reported since 2010. As shown in our series, of the 13 patients with grade II and III tumors in whom follow-up was available, only 4 (30.8%) received radiotherapy. This suggests unfamiliarity with these tumors on the part of both neurosurgeons and oncologists. It is now established that gross total resection decreases the risk of recurrence and increases survival in these tumors, and patients with grade II and III tumors benefit from adjuvant radiotherapy.[15],[16] The patients in this series were at a double disadvantage—gross total resection was not achieved in the majority of cases and the majority of patients did not receive adjuvant radiotherapy. The current 3-tiered grading system for meningeal SFT/HPCs may need to be modified in the future in order for a better correlation of the pathological grade to be established with the prognosis of these tumors. A comparison of the current study with the previous reported series is summarized in [Table 4].
Table 4: Summary of clinicopathological features of other studies conducted on meningeal solitary fibrous tumors confirmed with STAT-6

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 » Conclusion Top


In conclusion, these rare tumors need to be accurately diagnosed and optimally treated (by gross total resection and radiotherapy) to improve the prognosis. It is hoped that the current study will increase awareness regarding these rare tumors among pathologists, neurosurgeons, and oncologists in this part of the world so that patients can obtain an accurate diagnosis and benefit from the optimum management of these tumors.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
 » References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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