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Sinonasal tumours of varying histology are not unusual in otolaryngology surgical practice. Juvenile angiofibroma (JAs) are vascular tumours usually occurring in adolescent male population; but rare in females. But similar clinical and radiological presentations are possible in females inducing strong suspicion of JA which needs to be ruled out by detailed evaluation. Here we present a case of a young female in her 20s who presented with a bleeding nasal mass which was finally diagnosed as sinonasal glomangiopericytoma which is a very rare sinonasal tumour. Tumours resembling JA do present in the female population but rarely turn out to be JA. A strong index of suspicion along with a handful of special blood investigations to rule out androgen insensitivity syndrome is mandatory., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: Meningeal solitary fibrous tumour (SFT) and haemangiopericytoma (HPC) are uncommon tumours that have been merged into a single entity in the last 2021 WHO Classification of Tumors of the Central Nervous System. To describe the epidemiology of SFT/HPC operated in France and, to assess their incidence., Methods: We processed the French Brain Tumour Database (FBTDB) to conduct a nationwide population-based study of all histopathologically confirmed SFT/HPC between 2006 and 2015., Results: Our study included 399 SFT/HPC patients, operated in France between 2006 and 2015, in one of the 46 participating neurosurgical centres. The incidence reached 0.062, 95% CI[0.056-0.068] for 100,000 person-years. SFT accounted for 35.8% and, HPC for 64.2%. The ratio of SFT/HPC over meningioma operated during the same period was 0.013. SFT/HPC are about equally distributed in women and men (55.9% vs. 44.1%). For the whole population, mean age at surgery was 53.9 (SD ± 15.8) years. The incidence of SFT/HPC surgery increases with the age and, is maximal for the 50-55 years category. Benign SFT/HPC accounted for 65.16%, SFT/HPC of uncertain behaviour for 11.53% and malignant ones for 23.31%. The number of resection progresses as the histopathological behaviour became more aggressive. 6.7% of the patients with a benign SFT/HPC had a second surgery vs.16.6% in case of uncertain behaviour and, 28.4% for malignant SFT/HPC patients., Conclusion: Meningeal SFT and HPC are rare CNS mesenchymal tumours which both share common epidemiological characteristics, asserting their merging under a common entity. SFT/HPC incidence is less that one case for 1 billion per year and, for around 100 meningiomas-like tumours removed, one SFT/HPC may be diagnosed. SFT/HPC are equally distributed in women and men and, are mainly diagnosed around 50-55 years. The more aggressive the tumour, the higher the probability of recurrence., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Abstract: Sclerosing angiomatoid nodular transformation (SANT) is a reactive non-neoplastic, rare vascular lesion of the spleen. The histology shows multiple angiomatoid nodules surrounded by proliferative stroma. A 31-year-old lady presented with an abdominal mass for 6 months. Contrast-enhanced computed tomography (CECT) abdomen was suggestive of hemangiopericytoma/hemangioendothelioma. An open splenectomy was performed, and the resected specimen was sent for histopathology examination. The gross examination showed a bosselated mass present at the lower pole of the spleen measuring 8 × 8 cm with peripherally located coalescing red-brown nodules embedded in a dense fibrous stroma on the cut surface. On microscopy, multiple circumscribed angiomatoid nodules comprising irregular slit-like vascular channels lined by plump endothelial cells were seen embedded in dense sclerotic stroma. Because of the lack of specific diagnostic features, it is difficult to diagnose SANT clinically and radiologically. However, the typical histopathological findings are a clue in clinching the diagnosis., (Copyright © 2023 Copyright: © 2023 Indian Journal of Pathology and Microbiology.)

Objective: Solitary fibrous tumors (SFTs) and haemangiopericytomas (HPCs) are rare mesenchymal tumors in central nervous system (CNS). Although progressed recognition to the diagnosis and treatment of SFT/HPCs, it still remains many confusions regarding on its occurrence, aggressive evolution, malignant transformation, dedifferentiation phenomenon, distant metastasis and unpredictable propensity., Patients and Methods: Seventeen cases of CNS SFT/HPCs who underwent surgical treatment from January 2010 to December 2020 were collected in the authors' institute. Clinical, radiological, pathological data and followup details were reviewed in all cases., Results: The age of this series was 41-73 years old. Seven cases located subtentorially, five cases originated from middle skull base and four in supratentorial. MRI shows iso-signal intensity on T1WI, and heterogeneous slightly long/short signal on T2WI. There is significant contrast after gadolinium-enhancement. It is easy to be misdiagnosed before surgery. The positive rate of nuclear STAT6 is 94.12%, higher than CD34 (87.5%). Eight patients were grade I, eight grade II and one in grade III. Five cases developed tumor relapse, in which two cases had local intracranial recurrence combined with dissemination and metastasis of cerebrospinal fluid in the spinal canal, accompanied by pathological malignant transformation, and another one occurred blood metastasis., Conclusions: CNS SFT/HPCs are rare intracranial tumors with unpredictable propensity. Gross total resection is critical to its overall clinical prognosis. Given its potential recurrence and malignant transition, adjuvant radiotherapies are recommended when necessary, and long-term follow-up is indispensable. The underlying molecular biological mechanisms are still needed to be further exploration.

A 5-year-old girl presented with a 6-month history of strabismus and painless left proptosis. Magnetic resonance imaging revealed a homogenously enhancing, anterior, superomedial, left orbital mass. Excisional biopsy established the diagnosis of orbital glomangiopericytoma. Glomangiopericytoma of soft tissue is a perivascular myoid neoplasm with hemangiocytoma-like vascular channels that has overlapping features between glomus tumor and myopericytoma. To the authors' knowledge, glomangiopericytoma of the orbit has not previously been reported.

Background: Myopericytoma is a rare spindle cell tumor of mesenchymal origin, typically benign, characterized by concentric proliferation of tumor cells around blood vessels within subcutaneous tissue. It primarily occurs in middle-aged adults and is often located in distal extremities, although cases have been reported in proximal extremities and head-neck regions. However, occurrences within the oral cavity are exceedingly rare. To date, literature reviews have identified only two cases in children under 10 years old and reported only five cases of myopericytoma occurring in the lip region. We provide a comprehensive review and analysis of all documented cases to better understand this condition., Case Presentation: A 7-year-old girl presented to oral and maxillofacial surgery with the discovery of a painless mass on the inner aspect of the upper lip. The diagnosis of myopericytoma was confirmed by histological examination (HE staining), alcian blue staining, and immunohistochemistry., Conclusions: Following surgical excision, there were no signs of recurrence at a 3-month follow-up. The pathological diagnosis of myopericytoma is quite challenging, and immunohistochemical testing is necessary., (© 2024. The Author(s).)

Objectives: To present a case report of sinonasal glomangiopericytoma (GPC) in a female patient in her thirties and to highlight the importance of collecting pathology specimens even in routine sinus surgery cases., Methods: A case report detailing the diagnosis of GPC in a female in her thirties, including her initial presentation, treatment, and follow-up, along with a brief review of the literature., Results: Pathology of the collected specimen revealed sinonasal GPC along with chronic rhinosinusitis. Immunohistochemistry was positive for SMA, beta-catenin, and cyclin D1; and negative for STAT6, ERG, pankeratin, SOX10, and S100., Conclusion: This diagnosis expands the knowledge around the demographic profile of GPC patients. GPC should be included in the differential diagnosis of sinonasal masses, even in younger patients. The case highlights the importance of collecting the entire pathology specimen in all cases, even of ones that seem routine and benign., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: As the form of World Health Organization Central Nervous System (WHO CNS) tumor classifications is updated, there is a lack of research on outcomes for intracranial combined solitary-fibrous tumor and hemangiopericytoma (SFT/HPC). This study aimed to explore conditional survival (CS) pattern and develop a survival prediction tool for intracranial SFT/HPC patients., Methods: Data of intracranial SFT/HPC patients was gathered from the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute. The patients were split into training and validation groups at a 7:3 ratio for our analysis. CS is defined as the likelihood of surviving for a specified period of time (y years), given that the patient has survived x years after initial diagnosis. Then, we used this definition of CS to analyze the intracranial SFT/HPC patients. The least absolute shrinkage and selection operator (LASSO) regression and best subset regression (BSR) were employed to identify predictive factors. The Multivariate Cox regression analysis was applied to establish a novel CS-based nomogram, and a risk stratification system was developed using this model., Results: From the SEER database, 401 patients who were diagnosed with intracranial SFT/HPC between 2000 and 2019 were identified. Among them, 280 were included in the training group and 121 were included in the internal validation group for analysis. Our study revealed that in intracranial SFT/HPC, 5-year survival rates saw significant improvement ranging from 78% at initial diagnosis to rates of 83%, 87%, 90%, and 95% with each successive year after surviving for 1-4 years. The LASSO regression and BSR identified patient age, tumor behavior, surgery and radiotherapy as predictors of CS-based nomogram development. A risk stratification system was also successfully constructed to facilitate the identification of high-risk patients., Conclusion: The CS pattern of intracranial SFT/HPC patients was outlined, revealing a notable improvement in 5-year survival rates after an added period of survival. Our newly-established CS-based nomogram and risk stratification system can provide a real-time dynamic survival estimation and facilitate the identification of high-risk patients, allowing clinicians to better guide treatment decision for these patients., (© 2024. The Author(s).)

Solitary fibrous tumor/Hemangiopericytoma (SFT/HPC) is a rare subtype of soft tissue sarcoma harboring NAB2-STAT6 gene fusions. Mechanistic studies and therapeutic development on SFT/HPC are impeded by scarcity and lack of system models. In this study, we established and characterized a novel SFT/HPC patient-derived cell line (PDC), SFT-S1, and screened for potential drug candidates that could be repurposed for the treatment of SFT/HPC. Immunohistochemistry profiles of the PDC was consistent with the patient's tumor sample (CD99+/CD34+/desmin-). RNA sequencing, followed by Sanger sequencing confirmed the pathognomonic NAB2exon3-STAT6exon18 fusion in both the PDC and the original tumor. Transcriptomic data showed strong enrichment for oncogenic pathways (epithelial-mesenchymal transition, FGF, EGR1 and TGFβ signaling pathways) in the tumor. Whole genome sequencing identified potentially pathogenic somatic variants such as MAGEA10 and ABCA2. Among a panel of 14 targeted agents screened, dasatinib was identified to be the most potent small molecule inhibitor against the PDC (IC 50 , 473 nM), followed by osimertinib (IC 50 , 730 nM) and sunitinib (IC 50 , 1765 nM). Methylation profiling of the tumor suggests that this specific variant of SFT/HPC could lead to genome-wide hypomethylation. In conclusion, we established a novel PDC model of SFT/HPC with comprehensive characterization of its genomic, epigenomic and transcriptomic landscape, which can facilitate future preclinical studies of SFT/HPC, such as in vitro drug screening and in vivo drug testing., (© 2023. The Author(s) under exclusive licence to Japan Human Cell Society.)

Aims: To evaluate presenting features of patients with orbital solitary fibrous tumours (SFTs), based on histological phenotype., Methods: A retrospective case-note review was performed for demographics and presenting features for patients with orbital SFTs. The tumours were classified as "Group IA" hypocellular SFT phenotype, "Group IB" haemangiopericytoma phenotype and low mitotic activity, and high-grade "Group II" haemangiopericytoma phenotype with high mitotic activity., Results: Sixty-four patients (34 female; 53%) presented at a mean age of 42.2 years (median 38; range 19-82), with Group II patients presenting at an older age (mean 53 years). Median symptom duration was 12 months for Groups IA and IB, compared to 4 months for Group II, the commonest symptoms being proptosis (53%), diplopia (41%), periorbital swelling (31%), and altered vision (19%). Mean LogMAR was 0.17 (median 0.0; range -0.2-4), and 14% had ipsilateral optic neuropathy, with no significant difference between the three groups. Non-axial displacement was noted in 69%, a palpable mass in 45%, and reduced eye movements in 59%; choroidal folds and optic disc swelling were recorded in 12% and 9%. SFTs were mostly extraconal (59%), within the superior and superonasal quadrants (44%), with an average estimated tumour volume of 4.9 ml (median 3.6; range 0.31-14.5 ml)., Conclusion: SFTs may present with impaired visual function (∼15%), fundal abnormalities (a fifth), globe displacement (two-thirds), and reduced ocular motility (over a half). High-grade tumours tend to present more than a decade later, with a shorter duration of symptoms., (© 2023. Crown.)

Solitary fibrous tumor (SFT) is a rare type of mesenchymal lesion with variable clinical presentation in which specific clinicopathologic factors have been related to patient outcome. SFT shares an important morphologic and immunohistochemical overlap with other sarcomas, hence the differential diagnosis is challenging. Although molecular studies provide significant clues, especially in the differential diagnosis with other neoplasms, a thorough hematoxylin and eosin analysis and the integration of phenotypical, clinical, and radiological features remain an essential tool in SFT diagnosis. In this review, we discuss some emerging issues still under debate in SFT., (©The Author(s) 2023. Open Access. This article is licensed under a Creative Commons CC-BY International License.)

Objective: To review the research progress of intraspinal solitary fibrous tumor (SFT)., Methods: The domestic and foreign researches on intraspinal SFT were extensively reviewed and analyzed from four aspects, including disease origin, pathological and radiological characteristics, diagnosis and differential diagnosis, and treatment and prognosis., Results: SFT is an interstitial fibroblastic tumor with a low probability of occurrence in the central nervous system, especially in the spinal canal. In 2016, the World Health Organization (WHO) used the joint diagnostic term "SFT/hemangiopericytoma" according to the pathological characteristics of mesenchymal fibroblasts, which can be divided into three levels according to specific characteristics. The diagnosis process of intraspinal SFT is complex and tedious. It has relatively variable imaging manifestations and specific pathological changes of NAB2-STAT6 fusion gene, which often requires differential diagnosis with neurinoma, meningioma, etc . The treatment of SFT is mainly resection, which can be assisted by radiotherapy to improve the prognosis., Conclusion: Intraspinal SFT is a rare disease. Surgery is still the main treatment. It is recommended to combine preoperative or postoperative radiotherapy. The efficacy of chemotherapy is still unclear. In the future, more studies are expected to establish a systematic diagnosis and treatment strategy for intraspinal SFT.

Background: Solitary fibrous tumor/hemangiopericytoma (SFT/HPCT) is a rare tumor characterized by high recurrence rate and metastatic potential, even after surgical resection. We report on the clinical outcomes and risk factors for metastasis and progression-free survival (PFS) of patients diagnosed with SFT/HPCT., Methods: We retrospectively identified patients with intracranial or spinal SFT/HPCT who underwent surgical resection and/or radiation therapy at our institution between 1995 and 2021. Baseline demographics, tumor characteristics, and outcome data were collected, and factors associated with PFS and metastasis were analyzed., Results: Thirty-four subjects (mean age, 46.4 years; 44% female) with a histopathologically proven diagnosis of SFT/HPCT were included; the median follow-up was 89.7 months. Twenty-two tumors were supratentorial (67%), 6 (18%) were infratentorial, and 5 (15%) were spinal. Eleven patients had documented occurrence of metastasis (32%). Detailed preoperative and postoperative data were available for 25 patients (74%) who received treatment at our institution after their initial diagnosis. Of those, 20 (80%) underwent gross total resection (GTR), and 12 (48%) received either adjuvant or salvage radiotherapy. Univariate analyses revealed that males had a shorter mean PFS compared with females (25 months vs. 78 months; P = 0.01), and that patients who underwent GTR had a longer mean PFS compared with those who underwent subtotal resection (54 months vs. 23 months; P = 0.02). Male sex was the sole risk factor for metastasis (odds ratio, 6.75; 95% confidence interval, 1.19-38.02)., Conclusions: Our data demonstrate a strong association between male sex and the outcomes of shorter PFS and higher risk for metastases. Further research is warranted to understand the clinical characteristics and outcomes of this rare tumor., (Copyright © 2022 Elsevier Inc. All rights reserved.)

In the 2016 WHO classification of tumors of the central nervous system, hemangiopericytomas (HPCs) and solitary fibrous tumors (SFTs) were integrated into a new entity (SFT/HPC). Metastases to bone, liver, lung, and abdominal cavity are of concern. Only 37 cases of patients with liver metastases due to intracranial SFTs/HPCs have been reported. Herein, we present our experience in the management of patients with liver metastases from intracranial SFTs/HCPs. All consecutive patients who were treated for liver metastases from intracranial SFTs/HPCs from January 2014 to December 2020 were enrolled. Overall, three patients were treated for liver metastasis from SFTs/HPCs with curative intent. Two patients with bilobar metastases at presentation required surgical resection, transarterial embolization, stereotactic radiofrequency ablation (SRFA) and systemic therapy. One patient with a singular right liver lobe metastasis was treated with SRFA alone. This patient shows no evidence of liver metastases 39 months following diagnosis. Of the two patients with bilobar disease, one died 89 months following diagnosis, while one is still alive 73 months following diagnosis. Long-term survival can be achieved using a multimodal treatment concept, including surgery, loco-regional and systemic therapies. Referral to a specialized tertiary cancer center and comprehensive long-term follow-up examinations are essential.

Background: Hemangiopericytoma is a rare tumor of the sino-nasal tract. Its clinical behavior is controversial. Whereas some describe an indolent course, others consider it to be an aggressive lesion with a tendency toward rapid local recurrence. Here, we describe our experience in the management of sino-nasal hemangiopericytoma (SN-HPC), comparing our experience with the current literature, and evaluating signs and tools to improve diagnosis and treatment., Methods: All cases of SN-HPC between 2010 and 2020 were extracted and reviewed from our institutional electronic medical records. SN-HPC cases from PubMed and EMBASE between 2010 and 2020 were analyzed in a systematic literature review using the preferred reporting items for systematic review and meta-analysis (PRISMA) guidelines. Data regarding demographics, presentation, diagnosis, treatment, and outcome were collected., Results: We identified four cases of SN-HPC in the nasal cavity in our institution and an additional 53 cases in previous reports. The mean age at the time of diagnosis was 59 years, with a 1.2:1 male to female ratio. SN-HPC mostly appears unilaterally, arising in the ethmoid sinus (42.1%). The most common presenting symptoms were epistaxis (47.3) and nasal obstruction (47.3%). Both computed tomography (CT) and magnetic resonance imaging (MRI) were required for diagnosis and for tailoring the treatment plan. Endoscopic surgical excision was used in 85.9% of the patients, and in 15.7%, an additional preoperative embolization was performed, which was associated with septal necrosis in one patient (2.6%). The recurrence rate was 7%., Conclusion: Although previous reports attribute an aggressive tumoral behavior to SN-HPC, our experience and the literature review support a more indolent course with low recurrence rates following complete endoscopic resection. Preoperative embolization can be useful in certain cases, but due to potential complications, it should not be routinely indicated., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Myopericytomas are uncommon tumors defined by their round to spindle shaped cells often arranged in a concentric pattern of perivascular growth. They are typically well-circumscribed, nodular, slow-growing lesions that occur in the soft tissue of the extremities. Here, we present a 30-year-old female with a 2.4 cm myopericytoma occurring in the deep lobe of the parotid gland. The diagnosis was made with detailed histopathologic and immunohistochemical findings and positive identification of the specific mutation for PDGFRβ p.Asp666Lys by next generation sequencing (NGS). This is the first case report of a parotid myopericytoma with a genetic testing that shows a particular mutation that has been linked to myopericytomatosis.

Cerebral hemangiopericytomas are very rare mesenchymal tumours arising from pericytes surrounding the blood vessels in the brain. Most patients present with headaches, focal neurological findings and focal seizures with or without generalisation. Our patient chiefly complained of an uncontrollable movement of her right hand that was initially fleeting but later became continuous. Her symptoms were initially described as tremors. We found an intracranial tumour as a cause of her symptoms, suspected the tumour to be a meningioma and performed surgical extirpation which resulted in symptom resolution. Histopathology and immunohistochemistry of the excised mass revealed that the tumour was hemangiopericytoma. The patient is being closely monitored for recurrences and metastasis. Hemangiopericytomas are very rare and they rarely result in the abnormal movements of epilepsia partialis continua. Differentiation of the abnormal movements of epilepsia partialis continua from tremors is very important as is the differentiation of the tumour from meningioma., Keywords: case reports; epilepsia partialis continua; hemangiopericytoma; solitary fibrous tumors.

Meningiomas are common tumors of the central nervous system. Although their histological diagnosis is usually straightforward, their differential diagnosis versus other tumors may be challenging at times. The objective of this study is to assess the diagnostic value of CD13 immunoexpression in the differential diagnosis between meningiomas and their morphological mimics. Immunohistochemical analysis for CD13, epithelial membrane antigen, SOX10, and STAT6 was carried out in a large cohort of primary meningeal tumors comprising 225 meningiomas, 15 schwannomas, and 20 solitary fibrous tumor/hemangiopericytomas. Within the meningioma group, the expression of CD13 and epithelial membrane antigen was distinguished in three categories using a semiquantitative score. Most of meningiomas expressed CD13 (94%) and epithelial membrane antigen (96%) while none of the schwannomas nor of the solitary fibrous tumor/hemangiopericytomas was positive for either the two markers. Diffuse positivity for CD13 and epithelial membrane antigen was more common in low-grade meningiomas than in anaplastic ones, which were also more often negative for such markers, especially for CD13 (32%). CD13 is a helpful immunohistochemical marker for the differential diagnosis of meningiomas and their mimics, achieving in combination with epithelial membrane antigen maximal sensitivity (100%) and showing statistically relevant difference of expression in comparison with both schwannomas (p < 0.0001) and solitary fibrous tumor/hemangiopericytomas (p < 0.0001). Furthermore, loss of CD13 expression could be related to outcome as it is associated with worrisome histological findings, mainly in the setting of anaplastic meningiomas., (© 2022. The Author(s).)

A solitary fibrous tumour (SFT) is a mesenchymal tumour that exhibits fibroblast differentiation and rarely occurs in the retroperitoneum. The main purpose of this study was to explore the clinical manifestation, histopathological features and biological behaviour of retroperitoneal SFT. From 2011 to 2020, 31 patients were hospitalized and diagnosed with retroperitoneal SFTs. We summarized and analysed the morphological features, immunophenotype, treatment and prognosis. Patients (13 M; 18 F) ranged in age from 25 to 79 years with a mean age of 53.6 years. The main symptoms included an abdominal mass (48.4%) and abdominal discomfort (25.8%). The mean maximum diameter of the tumours was 12.9 cm (range, 4-40 cm). Histopathologically, there were 17 classic cases and 14 hemangiopericytoma-like cases. The tumour cells were positive for STAT6 (96.8%), CD34 (96.8%), CD99 (93.5%) and BCL-2 (90.3%). All patients were treated with complete surgical excision, and 3 of the patients also received chemotherapy. After a median follow up period of 44 months (range, 6 to 107 months), 2 patients died. Patients in the high- or intermediate-risk group were prone to metastasis and/or recurrence. The sites of metastases and/or recurrences involved the liver, bone and pelvis. The Ki-67 labelling index in the high-intermediate risk group (median, 10%) was significantly higher than that in the low-risk group (median, 3%). The retroperitoneal SFT demonstrates an indolent clinical course, and patients from the high- or intermediate-risk group require close follow-up. A Ki-67 labelling index ≥10% may be used as an important reference for prognosis.

Solitary fibrous tumor(SFT)/hemangiopericytoma(HPC)is a rare mesenchymal tumor with propensity for recurrence and metastasis. Although SFT and HPC were initially considered to be distinct entities, the identification of NAB2-STAT6 fusion as a definitive molecular alteration in both tumors has led to their integration into one disease entity, for both meningeal and non-meningeal lesions. This fusion leads to a nuclear relocation of the STAT6 protein and is detectable with immunohistochemistry. STAT6 immunohistochemistry has been shown to have excellent sensitivity and specificity for histological diagnosis. Although these discoveries have improved the diagnosis of SFT/HPC, the association of the NAB2-STAT6 fusion status with phenotype and prognosis remains unclear, and accurate prognostic factors have not been established. This comprehensive review provides current knowledge on the clinical, histological, and molecular characteristics of SFT/HPC.

An intracranial collision tumor is a rare lesion composed of two histologically different neoplasms in the same anatomic location. Even more rare is the collision tumor of a solitary fibrous tumor/hemangiopericytoma (SFT/HPC) and meningioma. The patient was a 46-year-old woman who had a 40 × 35 × 30-mm mass in the vermis of the cerebellum. Histologically, the mass consisted of two different components. One component showed the morphology of meningioma (World Health Organization (WHO) grade I), and the other component exhibited small round cell proliferation with hypercellular density, which was revealed to be SFT/HPC (WHO grade III) based on STAT6 immunohistochemistry. STAT6 showed completely different immunohistochemistry results in these two components (nuclear-negative in meningioma and nuclear-positive in SFT/HPC). Since these two neoplasms are associated with different prognoses, they should be distinguished from each other. When meningioma and an SFT/HPC-like lesion are identified morphologically, it is important to recognize the presence of such a collision tumor composed of meningioma and SFT/HPC, and identify the SFT/HPC component by employing STAT6 immunohistochemistry., (© 2021 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.)

Background: Infantile Hemangiopericytoma (HPC)/Solitary Fibrous Tumor (SFT), a vascular tumor of head and neck region, can be congenital or arise during the first year of the life. As the infantile form of hemangiopericytoma has a better course than the adult form, surgical excision is recommended. Case Report: A full-term neonate presented with a congenital right temporal soft tissue mass. MRI revealed a highly vascular mass with a hemorrhagic and possible necrotic core without intracranial extension. The lesion grew in 2 weeks from 4x4 cm to 9x7 cm. Histologically, a hypercellular spindle cell mesenchymal neoplasm had prominent staghorn vessels, alternating with hypocellular areas. Mitotic activity was low(1-3/HPF) and necrosis was absent. Conclusion: Infantile HPC/SFT of head and neck can grow rapidly during the infantile period. Complete excision without mutilating surgery should be curative.

Introduction: Meningeal solitary fibrous tumors (SFT), like all SFT, are defined by NAB2-STAT6 fusion and share clinicopathologic similarities with meningiomas, the most frequent meningeal tumors. Our aim is to establish the molecular identity of meningeal SFT and seek molecular prognostic factors., Methods: RNA sequencing and whole exome sequencing were performed in STAT6-positive SFT and grade 2-3 meningiomas, and data concerning other soft tissues tumors was obtained from the local database. Uniform manifold approximation and projection, individual gene expression and Gene Set Enrichment Analysis were performed., Results: RNA clustering shows that SFT share a common molecular signature, different from any other type of tumoral tissue. Meningeal SFT aggregate with other SFT, with no clinical or histological subgroup. Comparison of genes expressions suggests significant over-expressions of ZIC2, ZIC3, ZIC5, GABBR2, TP53 in CNS-SFT. The pathogenic TP53 c.743G>T variant, previously undescribed in SFT, was found in one sample of meningeal SFT during malignant progression., Conclusions: Meningeal SFT are molecular counterparts of extra-meningeal SFT, completely separate from meningiomas. They might develop from the same tissues and benefit from the same treatments as SFT., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: Hemangiopericytomas (HPCs) and solitary fibrous tumors (SFTs) are rare tumors of mesenchymal origin. Here, the authors present a rare case of anaplastic HPC in the jugular foramen (JF). The authors also conduct a systematic review of the literature to examine the current fund of knowledge on JF HPC/SFTs., Methods: A systematic MEDLINE search was conducted using key words "hemangiopericytoma" OR "solitary fibrous tumor" AND "jugular foramen" OR "extracranial" OR "skull base." Clinicopathologic characteristics and outcomes of the present case were reviewed and compared with those in the literature., Results: A 41-year-old male, who had undergone stereotactic radiation therapy 6 years ago for a presumed glomus jugulare tumor, presented to our institution with worsening dysphagia, hoarseness, persistent tongue weakness, and radiographic evidence of tumor progression. The patient underwent uncomplicated gross total resection with sacrifice of the infiltrated hypoglossal nerve. Histopathologic evaluation revealed anaplastic HPC/SFT (World Health Organization grade III). Review of the literature yielded 9 additional cases of JF HPC/SFT in 5 males (56%) and 4 females (44%), with a mean age of 49.6 years old. Patients commonly presented with pain (37.5%) and lower cranial nerve deficits (100%). Preoperative diagnoses included glomus jugulare (n = 2) or JF schwannomas (n = 3). All patients underwent microsurgical resection of the lesion, except for 1 who refused all treatment after diagnostic biopsy., Conclusion: The authors present the only reported case of anaplastic HPC of the JF. The illustrative case and those found on systematic review of the literature highlight the importance of tissue diagnosis and appropriate management., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Intracranial hemangiopericytoma is a rare disease and surgery is the mainstay treatment. Although postoperative adjuvant radiotherapy is often used, there are no reports comparing different radiotherapy techniques. The purpose of this study is to analyze the impact of post-operative radiotherapy and different radiotherapy technique on the results in patients with intracranial hemangiopericytoma (HPC)., Methods: We retrospectively reviewed 66 intracranial HPC patients treated between 1999 and 2019 including 29 with surgery followed by radiotherapy (11 with intensity-modulated radiotherapy (IMRT) and 18 with stereotactic radiosurgery (SRS)) and 37 with surgery alone. Chi-square test was used to compare the clinical characteristic between the groups. The Kaplan-Meier method was used to analyze overall survival (OS) and recurrence-free survival (RFS). Multivariate Cox proportional hazards models were used to examine prognostic factors of survival. We also underwent a matched-pair analysis by using the propensity score method., Results: The crude local control rates were 58.6% in the surgery plus post-operative radiotherapy group (PORT) and 67.6% in the surgery alone group (p = 0.453). In the subgroup analysis of the PORT patients, local controls were 72.7% in the IMRT group and 50% in the SRS group (p = 0.228). The median OS in the PORT and surgery groups were 122 months and 98 months, respectively (p = 0.169). The median RFS was 96 months in the PORT group and 72 months in the surgery alone group (p = 0.714). Regarding radiotherapy technique, the median OS and RFS of the SRS group were not significantly different from those in the IMRT group (p = 0.256, 0.960). The median RFS were 112 and 72 months for pathology grade II and III patients, respectively (p = 0.001). Propensity score matching did not change the observed results., Conclusion: In this retrospective analysis, PORT did not improve the local control rates nor the survivals. The local control rates after IMRT and SRS were similar even though the IMRT technique had a much higher biological dose compared with the SRS technique., (© 2021. The Author(s).)

Objectives: Intracranial solitary fibrous tumor/hemangiopericytoma (SFT/HPC) is a rare mesenchymal neoplasm with imaging features mimicking high-grade meningioma (HGM) and can easily be misdiagnosed. We sought to determine the value of routine preoperative data in differentiating these tumors., Patients and Methods: Patients with confirmed SFT/HPC or HGM between January 2012 and June 2020 were identified. A total of 28 preoperative variables (including age, sex, tumor location, tumor volume, 10 traditional MRI features, and 14 peripheral blood indices) were collected for each patient. The top features were selected sequentially based on the least absolute shrinkage and selection operator (LASSO) and support vector machines-recursive feature elimination (SVM-RFE) methods. Differentiation and calibration of the classifiers were assessed by receiver operating characteristic (ROC) curves and calibration curves, respectively. Nomograms were constructed based on multivariate analysis., Results: A total of 127 patients, including 29 with SFT/HPC and 98 with HGM, were analyzed. Three features were first selected using the LASSO and SVM-RFE methods, and corresponding models were developed. Although the area under the curve (AUC) of model 1 was the highest, a comprehensive analysis suggested the superiority of model 2, which consisted only of the features tumor volume (TV) and dural tail sign (DTS) (AUC: 0.942, sensitivity: 93.10%, p-value of H-L test: 0.734, Brier score: 0.07). A risk score formula and a nomogram were constructed., Conclusions: TV can be used to effectively identify SFT/HPC and HGM, whereas adding DTS can improve the overall prediction accuracy. As these two variables are routinely available and are easy for clinicians to master, they can provide a powerful reference for clinical decision-making., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Published risk stratification models of solitary fibrous tumor (SFT) have been associated with distant metastases outside the central nervous system (CNS), but have not been studied for tumors occurring in the CNS. In a retrospective review, we identified 72 cases of solitary fibrous tumor or hemangiopericytoma (HPC) diagnosed between January 2011 and December 2020 at our institution. The tumors involved the central nervous system (N = 17), thoracic cavity (N = 28), and extrathoracic sites (N = 27). The risk of local recurrence, distant metastasis, or death at 5 years was 57% (95% CI 23%, 76%) in the CNS, 24% (95% CI 2%, 41%) in the thoracic cavity, and 13% (95% CI 0%, 25%) in extrathoracic sites. By contrast, the risk of distant metastasis or death at 5 years was 13% (95% CI 0%, 29%) in CNS primaries, 5% (95% CI 0%, 14%) in thoracic primaries, and 14% (95% CI 0%, 27%) in extrathoracic primaries. Using the published 3- and 4-variable risk stratification models by Demicco et al., we retrospectively assessed our cases for risk of local recurrence, distant metastasis, and death. For tumors outside the CNS, we show that three- and four-variable risk stratification models were associated with recurrence-free survival in addition to the previously known association with distant metastasis (all P < 0.05). In contrast, inside the CNS, we show that neither risk model is a significantly associated with clinical behavior, and that WHO grade is likely the best available prognostic tool, though none of the differences were significant. The lack of significant differences can be likely explained by the younger median age (47 years vs 61 years) and smaller median tumor size (3.5 cm vs 5.6 cm), downgrading the risk stratification scores in CNS compared to non-CNS primaries. In conclusion, existing risk stratification models of SFT are not associated with clinical behavior for tumors arising inside the CNS, but are associated with local recurrence in addition to distant metastasis outside the CNS., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

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.

Solitary fibrous tumor (SFT) is an uncommon mesenchymal tumor of fibroblastic origin, which shows a prominent hemangiopericytoma-like branching pattern. It may be found at any location and can rarely involve the female genital tract with the vulva being the most common site of involvement. This is a case report of vulvar SFT in a 47-yr-old female who presented with a slow growing vulvar mass for 3 yr. Histologic examination showed a neoplasm composed of ovoid to spindle shaped cells with hypocellular and hypercellular areas in a collagenous background. Prominent hemangiopericytoma-like vessels were identified. Immunohistochemistry showed positive staining of the tumor cells for CD34, STAT6, ER, PR, and vimentin. Immunoshistochemical staining for desmin, SMA, and S100 was negative. The majority of SFTs have a NAB2-STAT6 gene fusion on chromosome 12, resulting in nuclear STAT6 overexpression, which is a sensitive and specific immunohistochemical marker for its diagnosis. Only 25 cases of vulvar SFT have been reported in the English literature and it should be considered in the differential diagnosis of spindle cell lesions at this site., Competing Interests: The author declares no conflict of interest., (Copyright © 2020 by the International Society of Gynecological Pathologists.)

Meningeal solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) were categorized as the same entity in the World Health Organization (WHO) 2016 classification of tumors of the central nervous system (CNS). Although NAB2-STAT6 fusion protein can be used to distinguish most of SFT/HPC from the other sarcomas, additional biomarkers were requested to separate meningeal SFT/HPC from meningioma and the molecular pathological difference between meningeal SFT/HPC and extra-CNS SFT/HPC still remains unclear. In this study, we evaluated the expression of TTF-1 in 67 meningeal SFT/HPC, 62 extra-CNS SFT/HPC and 201 meningiomas samples with immunohistochemistry (IHC) assays. The results showed that TTF-1 was detected in 23 of 67 (34.3%) meningeal SFT/HPC, 3 retroperitoneum SFT/HPC and none of meningiomas. Meanwhile, the copy number variation and mRNA expression of TTF-1 were measured by real-time quantitative PCR (qPCR) in meningeal SFT/HPC. These results demonstrated that TTF-1 protein expression level was significantly correlated with its transcription level, but independently related to the gene copy number variant. In conclusion, our study suggested that a large proportion of meningeal SFT/HPC was positive to TTF-1, while very few extra CNS SFT/HPC cases and no meningiomas were stained. So TTF-1 has value as an auxiliary diagnostic marker for meningeal SFT/HPC.

Hemangiopericytoma (HPC) is a rare vascular tumour and difficult to diagnose clinically. Incidence is reported in fourth to fifth decade of life.With female predominance, 3%-5% cases affect the oral cavity, sinus lining and meninges. The patient presented with 8×6 cm swelling on her face, evaluation reported it to be HPC. Bilateral maxillary artery embolisation, wide local excision of the lesion, preserving the left eye and its function, was done. No recurrence is reported at 1-year follow-up. Response of such lesions to radiotherapy is questionable; with no lymphadenopathy and adequate encapsulation, embolisation of feeder vessel followed by a wide local excision of the lesion seems to be a fairly good option of treatment., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Since the discovery of the NAB2-STAT6 gene fusion in 2013, solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) have been considered the same disease. STAT6 nuclear stain is approved as a highly sensitive and specific marker to diagnose SFT/HPC from other tumors with similar histology. As the next step, detection of fusion variants that may predict clinical malignancy of SFT/HPC has been attempted. However, no fusion variants with a clear relation to malignancy have been identified. In this study, the clinical and histological backgrounds of 23 Japanese patients diagnosed with SFT/HPC from 2000 to 2019 at Kochi University Hospital were examined to identify factors potentially related to recurrence. A significant relationship to recurrence was detected for mitosis ≥ 1/10 HPF (400×), necrosis, and Ki-67>5%. These findings indicate that a deliberate investigation of histological features such as mitosis and necrosis is crucial for the clinical observation of SFT/ HPC patients. In addition, Ki-67 was revealed to be a useful parameter to predict recurrence in SFT/HPC patients., Competing Interests: No potential conflict of interest relevant to this article was reported.

Sinonasal glomangiopericytoma (GPC) is an uncommon primary sinonasal neoplasm showing a perivascular myoid differentiation. Originally perceived as an intranasal counterpart to soft tissue hemangiopericytomas, initial immunohistochemical reports showed mostly negative to focal weak reactivity for CD34 as useful in separating GPC (almost always benign) from morphologic mimics, mainly solitary fibrous tumor (potentially aggressive). In anecdotally encountering cases of GPC with CD34 reactivity beyond the expected weak/negative immunoprofile, we sought to formally evaluate CD34 staining in 10 cases of GPC from two different vendors in conjunction with a meta-analysis of other GPC series reporting CD34 staining. Ten cases of GPC were retrieved from the authors' pathology archives (left nasal cavity = 7, right nasal cavity = 3; 5 men, 5 women; average age 59.0 years with range of 43-77 years). Follow-up showed no evidence of disease after complete resection from all 10 cases (average follow-up length of 53.3 months, range 6-106 months). All 10 GPC cases (100%) showed positivity using CD34 from Leica (QBend10 clone), with most showing moderate to diffuse staining intensity and moderate extent, while only 2 of 10 cases (20%) showed positivity using CD34 from Ventana (QBend10 clone), with both positive cases showing weak staining intensity and focal extent. Literature review of other studies (reporting ≥ 5 GPC cases) found a wide spectrum of CD34 positivity ranging from 0 to 100%; including our GPC cases, CD34 showed a cumulative positivity of 28%. Although negative CD34 reactivity has been historically regarded as prototypic for GPC, in this study we have exposed laboratory variability in CD34 expression and have shown that reliance on expected negative reactivity in GPC can be a clinically relevant diagnostic pitfall. Our findings suggest a panel approach in selecting diagnostic immunostains rather than relying on CD34 alone in the assessment of spindle cell neoplasms in the sinonasal tract with admixed prominent staghorn-like vasculature.

Rationale: Intracranial solitary fibrous tumors (SFTs) and hemangiopericytomas (HPCs) are rare spindle cell tumors of mesenchymal origin that include benign and malignant neoplasms., Patient Concerns: We present a 66-year-old male with a 5-year history of headache and dizziness, with left progressive sensorineural hearing loss over 1 month., Diagnoses: WHO grade II SFT/HPC originating from the internal auditory canal in the left cerebellopontine angle., Interventions: surgical resection., Outcomes: No local recurrence or metastases were observed in the follow-up 3 months after the surgery., Lessons: Intracranial SFTs/HPCs are rare mesenchymal neoplasms that are challenging to manage. If the imaging characteristics of tumor are not typical, clinicians should depend on tissue biopsy and immunohistochemistry to make a definitive diagnosis.

Introduction: Tumors of the spinal cord are rare and some can be confused with each other. We report a rare spinal cord solitary fibrous tumor/hemangiopericytoma (SFT/HPC), and propose keys to differentiate spinal cord tumors from each other., Case Report: A 67-year-old man presented weakness with recent diffuse sensory disorders in the right lower limb. Spinal MRI revealed a T8-T9 intradural extramedullary mass with spinal cord compression. Gross total resection of a poorly vascularized intradural tumor was achieved. It was an encapsulated extramedullary tumor, which was difficult to separate from the spinal cord due to the presence of pial adhesions. Definitive diagnosis was grade 1 SFT/HPC of the spinal cord. One-year follow-up MRI revealed complete excision without any evidence of residual tumor., Conclusion: SFT/HPC is a very rare spinal tumor that can be extramedullary, intramedullary or both. It may perfectly mimic meningioma. The maximal resection is the best treatment, but can be challenging because of the tumor's firm consistency and pial adherences to the spinal cord. Outcome is good in case of gross total resection, but there is a risk of very late recurrence, requiring long-term follow-up., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

The solitary fibrous tumor/ hemangiopericytoma (TFS/HP) is a rare mesenchymal extraaxial tumour. TFS/HP can sometimes be difficult to distinguish from other extra-axial tumors like meningioma, which can be clinically and radiologically indistinguishable. Molecular analysis with STAT6 (signal transducer and activator of transcription 6) nuclear expression or NAB2-STAT6 (NGFI-A binding protein 2) fusion is recommended to confirm the diagnosis. We present 3 cases, 2 women and 1 male, with pathological diagnosis of meningothelial meningioma in the first case; cases 2 and 3 with radiological suspicion of meningioma. The pathological review with molecular study certified the diagnosis of TFS/HP. For differential diagnosis between meningeal TFS/HP and meningioma, it is recommended to look for STAT6 expression as a first step, or NAB2-STAT6 fusion in order to confirm TFS/HP. The review of biopsy samples must be guaranteed in all patients, including those who were studied in Pathology Services Level 3.

Background/aim: Extralobar pulmonary sequestration (EPS) is an unusual congenital defect characterized by the presence of non-functioning lung tissue receiving arterial supply from the systemic arteries. Primary hemangiopericytoma (HPC) is an uncommon potentially malignant tumor of vascular origin that usually involves the soft tissue of the extremities or retroperitoneum, but extremely rarely affects the lung. We present the rare case of a primary pulmonary HPC arising in an EPS., Case Report: A 65-year-old woman, with dyspnea and pleuritic chest pain, was referred for further investigation. Radiological evaluation demonstrated a well-circumscribed mass above the right hemidiaphragm, receiving its arterial supply from the descending thoracic aorta. The patient underwent a right posterolateral thoracotomy and a middle lobectomy. The intraoperative finding was a well-encapsulated solid mass. The histological evaluation described HPC., Results: The patient remains fit and healthy., Conclusion: Pulmonary HPC can arise in EPS. Surgical excision is the treatment of choice., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Objective: Solitary fibrous tumor/hemangiopericytoma (SFT/HPC) and meningioma exhibit similar radiographic features; however, they differ in their prognoses. Preoperative differentiation between them is important for determining the treatment and follow-up plan. The aim of this study was to determine the factors that can be used to differentiate SFT/HPC from meningioma and World Health Organization (WHO) grade I from grade II meningioma., Methods: The analysis included 84 cases: 5 of SFT/HPC, 72 of WHO grade I meningioma, and 7 of WHO grade II meningioma. Clinical characteristics and conventional magnetic resonance imaging, perfusion magnetic resonance imaging, and magnetic resonance spectroscopy (MRS) LCModel parameters were evaluated via multivariate logistic regression analysis to identify the factors that distinguish SFT/HPC from meningioma., Results: Patients with SFT/HPC were mostly men and were younger than those with meningioma. The percentage of T2-weighted images in meningioma was greater than that in SFT/HPC. There were significant differences between SFT/HPC and meningioma in levels of glutamate, phosphocholine, myo-inositol, or glycerophosphocholine + phosphocholine derived from long echo-time MRS, and myo-inositol derived from short echo-time MRS. Stepwise logistic regression analysis revealed that the age of <45 years and myo-inositol in short echo-time MRS of ≧6.347 were associated with a diagnosis of SFT/HPC with high sensitivity and specificity. However, no factors were found that differentiated WHO grade I meningioma from WHO grade II meningioma., Conclusions: Age and myo-inositol level calculated from MRS are useful factors for distinguishing SFT/HPC from meningioma preoperatively., (Copyright © 2019 Elsevier Inc. All rights reserved.)

To study the clinicopathologic characteristics,immunohistochemical features,differential diagnosis,and prognosis of solitary fibrous tumours(SFT)/hemangiopericytomas(HPC)in the maters(meninx). Methods A series of 7 cases previously diagnosed as SFT/HPC at the Department of Pathology,Peking Union Medical College Hospital,during the period from 2008 to 2018 were analyzed for clinical data,histopathology,and immunohistochemical findings.The patients were followed up and the relevant literatures were reviewed. Results These seven patients included two males and 5 females aged 22 to 77 years(mean,49 years).Headache was the most common symptom.The magnetic resonance imaging of SFT/HPC showed irregularly contoured masses and dural tail sign was observed at the periphery of the lesion in 4 cases.The major axis of the tumor ranged from 1.8 cm to 10 cm(mean,4 cm).The tumors were located in the mater in 6 cases and in the spinal meninx in 1 case.The tumors were surgically removed in all cases.Under light microscope,the tumors were formed by long round,oval or spindle cells,with rich branching vascular pattern and varying quantity of collagenous fibers bands in both sparse areas and dense areas.According the WHO classification,2 cases were in WHO grade Ⅰ,2 cases in WHO grade Ⅱ,and 3 cases in WHO grade Ⅲ.Immunohistochemistry of the paraffin-embedded tissues in all cases showed positive immunoreativity for CD34 and vimentin in all seven cases,along with positive signal transducer and activator of transcription 6 in 4 cases,negative epithelial membrane antigen and S-100 in 7 cases,and negative progestational hormone and somatostatin receptor 2 in 6 cases.The Ki-67 index ranged from 1% to 15%.Five patients with follow-up data(including 1 current case)were alive,while 2 patients were lost to follow-up. Conclusions The SFT/HPC are rare in the maters(meninx)and is clinically difficult to be differentiated from other meningioma.The combination of CD34 and signal transducer and activator of transcription 6 helps to diagnose this disease.

Background: Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm affecting soft tissues with a not well defined biological behavior. SFT occurs mostly in the pleura and the thorax, while extra-thoracic localization is uncommon and abdominal localization is very rare. Histologically, SFT is a well defined mass with splindle-cell proliferation in collagenous matrix with staghorn vascular network and CD34 reactive., Case Report: A 64 years-old man with a history of recurrent gastric cancer previously treated with total gastrectomy, was admitted with contrast enhanced CT-scan diagnosis of a well demarcated oval mass of 4.8 cm with microcysts, vascularized in the arterial phase and with wash out in the tardive phase, located in the peritoneal side of right rectus abdominis muscle, suspected for metastatic gastric tumor. The patient underwent minilaparotomy and en-bloc excision of the lesion. Histologically the tumor was characterized by a hemangiopericitoma like growth pattern and the immunostaining was positive to CD34, CD99, BCL-2 and Vimentin. The definitive diagnosis was SFT with a proliferation index (Ki-67/MIB-1) <3%. In our case, chemotherapy was not indicated. At the 6-month follow-up, the patient is in good clinical conditions with no recurrence or metastasis., Conclusions: We reported a rare case of primitive SFT located in peritoneal side of the of right rectus abdominis muscle treated surgically, in a patient previously affected by gastric adenocarcinoma. In this case, SFT showed a benign behaviour during a short term follow-up. Dimensional pattern, histopathological features and curative surgery remain the most important indicators of clinical outcome., Key Words: Abdominal wall, Hemangiopericitoma, SFT, Solitary fibrous tumorSpindle cell.