Extra-thoracic, extra-meningeal solitary fibrous tumours - A case series and service review

Published:November 02, 2021DOI:https://doi.org/10.1016/j.jcot.2021.101675

      Abstract

      Background

      Solitary fibrous tumours (SFT) are a type of mesenchymal tumour. Whilst the majority of cases follow an indolent course a significant proportion of patients suffer metastases or disease recurrence post-surgical excision. Due to the unpredictable clinical course follow up duration and intensity remains contentious.

      Aims

      We aimed to determine current outcomes of management of this tumour, apply and assess current risk recurrence models to determine if our standard of care could be improved upon.

      Methods and patients

      A prospective database of patients treated at a regional musculoskeletal oncology service was assessed. Only extra-pleural, extra-meningeal SFTs were included in the study. Surgical outcome and post-operative investigations were scrutinised and the Pasquali and Demicco recurrence risk models were applied and assessed.

      Results

      From 2009 to 2019 12 patients were identified, 8 female and 4 males. Their age at diagnosis ranged from 21 to 76 years. 11 patients underwent surgery with curative intent and no patient suffered disease progression or recurrence, with a mean follow up time of 41 months. One patient presented with metastatic disease and was managed palliatively.

      Conclusions

      Following this review of our case series and utilising risk recurrence models published in the literature we have changed our follow up protocol. In new cases of SFT the Pasquali prognostic model, with the addition of the presence or absence of necrosis, will be utilised. If a patient has benign features on initial biopsy we propose to not perform staging. Furthermore, if biopsy and final pathology results remain concordant, with no concerning features, and the patient has undergone complete excision reduced intensity follow up could be considered.Level of evidence Level IV, retrospective case series.

      Keywords

      1. Introduction

      Solitary fibrous tumours (SFT) are a type of mesenchymal tumour. They were previously thought to occur predominantly within the thorax, but are now known to occur as frequently in extra-thoracic locations.
      • De Perrot M.
      • Fischer S.
      • Bründler M.A.
      • Sekine Y.
      • Keshavjee S.
      Solitary fibrous tumors of the pleura.
      • Guo W.
      • Xiao H.L.
      • Jiang Y.G.
      • et al.
      Retrospective analysis for thirty-nine patients with solitary fibrous tumor of pleura and review of the literature.
      • Van Houdt W.J.
      • Westerveld C.M.A.
      • Vrijenhoek J.E.P.
      • et al.
      Prognosis of solitary fibrous tumors: a multicenter study.
      Previously SFTs were termed haemangiopericytoma, until 2002 when the third WHO classification of soft tissue tumours grouped extra-meningeal SFTs, haemangiopericytoma, lipomatous haemangiopericytoma and giant cell angiofibroma within the spectrum of extrapleural SFT.
      • World Health Organization
      Pathology & Genetics Tumours of Soft Tissue and Bone.
      The recurrent gene fusion NAB2-STAT6 on chromosome 12q13 was identified from whole exome sequencing data as a unique mutation to SFTs.
      • Chmielecki J.
      • Crago A.M.
      • Rosenberg M.
      • et al.
      Whole-exome sequencing identifies a recurrent NAB2-STAT6 fusion in solitary fibrous tumors.
      ,
      • Robinson D.R.
      • Wu Y.M.
      • Kalyana-Sundaram S.
      • et al.
      Identification of recurrent NAB2-STAT6 gene fusions in solitary fibrous tumor by integrative sequencing.
      SFTs arise from spindle cells and histopathologically range from low grade to malignant and high grade.
      • Musyoki F.N.
      • Nahal A.
      • Powell T.I.
      Solitary fibrous tumor: an update on the spectrum of extrapleural manifestations.
      Accordingly, the majority of the tumours follow a benign course. However, a significant proportion of patients suffer disease progression, with distant metastases described to many sites inclusive of lung, liver and bone.
      • Vallat-Decouvelaere A.V.
      • Dry S.M.
      • Fletcher C.D.M.
      Atypical and malignant solitary fibrous tumors in extrathoracic locations: evidence of their comparability to intra-thoracic tumors.
      A recent multi-centre study of extra-thoracic and extra-meningeal SFTs reported an 18.5% recurrence rate, with the majority of these recurrences occurring distally from the primary tumour site.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      Traditional sarcoma staging systems, such as the American Joint Committee on Cancer staging, have not been validated for predicting the behaviour of SFTs.
      • Mosquera J.-M.
      • Fletcher C.D.M.
      Expanding the spectrum of malignant progression in solitary fibrous tumors.
      The majority of SFTs follow an indolent course, however, a small but significant proportion of cases demonstrate overt sarcomatous transformation. Therefore, the behaviour of SFTs is commonly described as unpredictable.
      • McMaster M.J.
      • Soule E.H.
      • Ivins J.C.
      Hemangiopericytoma: A Clinicopathologic Study and Long-term Followup of 60 Patients.
      The main modality of treatment for SFTs is surgical excision, aiming to achieve complete resection with negative margins. The use of adjuvant therapy is not commonly utilised with conventional chemotherapy regimens, such as anthracyclines, shown to not improve outcomes.
      • Constantinidou A.
      • Jones R.L.
      • Olmos D.
      • et al.
      Conventional anthracycline-based chemotherapy has limited efficacy in solitary fibrous tumour.
      Chemotherapy and radiotherapy are more often used in metastatic disease or in cases with positive margins post excision,.
      • Musyoki F.N.
      • Nahal A.
      • Powell T.I.
      Solitary fibrous tumor: an update on the spectrum of extrapleural manifestations.
      ,
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      A recent large retrospective, international study of SFTs of all extrameningeal locations demonstrated improved local disease control, without survival benefit, with the use of adjuvant radiotherapy.
      • Haas R.L.
      • Walraven I.
      • Lecointe-Artzner E.
      • et al.
      Extrameningeal Solitary Fibrous Tumors—Surgery Alone or Surgery Plus Perioperative Radiotherapy: A Retrospective Study from the Global Solitary Fibrous Tumor Initiative in Collaboration with the Sarcoma Patients EuroNet.
      Marginal excision is often reported, this has been attributed to SFTs commonly being deep seated with the presence of large collateral feeding vessels.
      • Robinson D.R.
      • Wu Y.M.
      • Kalyana-Sundaram S.
      • et al.
      Identification of recurrent NAB2-STAT6 gene fusions in solitary fibrous tumor by integrative sequencing.
      Metastatic disease has also been reported to occur several years post successful surgery.
      • Vallat-Decouvelaere A.V.
      • Dry S.M.
      • Fletcher C.D.M.
      Atypical and malignant solitary fibrous tumors in extrathoracic locations: evidence of their comparability to intra-thoracic tumors.
      ,
      • Gronchi A.
      • Miceli R.
      • Allard M.A.
      • et al.
      Personalizing the approach to retroperitoneal soft tissue sarcoma: histology-specific patterns of failure and postrelapse outcome after primary extended resection.
      ,
      • Trojani M.
      • Contesso G.
      • Coindre J.M.
      • et al.
      Soft-tissue sarcomas of adults; study of pathological prognostic variables and definition of a histopathological grading system.
      Due to the above factors follow up post-surgery often advocates reviews over a long period of time, inclusive of local examination and chest surveillance imaging.
      It is evident that the clinical course of patients suffering from SFTs is highly unpredictable and follow up duration and intensity remains contentious. Several studies have proposed risk recurrence models, in order to stratify intensity and duration of follow-up for patients suffering this disease.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      ,
      • Demicco E.G.
      • Wagner M.J.
      • Maki R.G.
      • et al.
      Risk assessment in solitary fibrous tumors: validation and refinement of a risk stratification model.
      We performed a review of all cases of SFT within our tertiary referral musculoskeletal oncology centre. We aimed to determine current outcomes of management of this tumour, apply and assess current risk recurrence models and determine if our standard of care could be improved upon.

      2. Methods

      A prospective database of patients treated at a regional musculoskeletal oncology service was assessed. All patients managed within the service with a diagnosis of SFT were identified between the years of 2010 and 2019. Only patients with a histological diagnosis, from biopsy and excision, of SFT were included. Only extra-pleural, extra-meningeal SFTs were included in the study. The tumour size and location and extent of preoperative staging was assessed. Tumour characteristics including presence of necrosis, cellularity, mitotic rate and degree of pleomorphism were assessed for each patient. The type of surgical excision, and tumour margins achieved was assessed along with the use of any adjuvant therapies. Post-operative records and investigations were scrutinised to determine outcomes of management of the disease for each patient.
      To determine whether the services post-operative management could be improved upon two recurrence risk models for SFT were applied to the cohort.

      3. Results

      12 patients were treated for SFT within our centre between 2009 and 2019. 8 were female and the mean age at diagnosis was 53 years (range 21–76 years). Locations and tumour indices are included in Table 3, Table 4. All patients underwent image guided biopsy. Mean tumour size was 7.7 cm (range 2.2–16 cm). 9 patients underwent staging with computerised tomography (CT) scanning of chest, abdomen and pelvis. No discrepancy was observed between the pre-operative biopsy diagnosis and post-operative tumour specimen. Fig. 1 demonstrates pre-operative magnetic resonance imaging (MRI) of a patient within the series.
      Fig. 1
      Fig. 1Coronal and axial pre-operative MRI scan of a patient with a benign SFT of the thigh.
      One patient presented with distant bony and pulmonary metastases at time of diagnosis and was managed palliatively, their biopsy confirmed a malignant SFT. The remaining 11 patients were treated with curative intent with complete tumour excision.
      No neoadjuvant or adjuvant therapy was utilised in addition to tumour resection. One patient presented with distal metastases. She underwent palliative chemotherapy followed by prophylactic intra-medullary nailing of a femur and open reduction and internal fixation of a humerus for metastatic bone disease. This patient died 18 months after diagnosis.
      The overall survival of the cohort is a median of 58 months (range of 11–141 months). Of the 11 patients managed with curative intent complete excision was achieved in all the primary operations. No local recurrences or distant metastases have occurred. 6 patients underwent chest surveillance at follow up via chest radiographs. The mean follow-up post operation was 41 months. 4 patients remain under active follow up.
      Pasquali et al.’s SFT recurrence risk model, Table 1, was applied.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      Recurrence risk was categorized as very low, low, intermediate and high in 2 (16.7%), 7 (58.3%), 2 (16.7%) and 1 (8.3%) respectively. The patient who presented with metastatic disease was identified as high risk.
      Table 1Pasquali et al. recurrence risk model. Tumour indices and risk of recurrence displayed.
      • Mosquera J.-M.
      • Fletcher C.D.M.
      Expanding the spectrum of malignant progression in solitary fibrous tumors.
      VariablesScore
      Mitotic rateLow

      High (>4 x HPF)
      0

      3
      CellularityLow

      Moderate - High
      0

      2
      PleomorphismLow

      Moderate - High
      0

      2
      Recurrence RiskTotal score
      Very low0
      Low2
      Intermediate3–5
      High>5
      Subsequently the recurrence risk stratification scheme by Demicco et al., Table 2, was applied.
      • Demicco E.G.
      • Wagner M.J.
      • Maki R.G.
      • et al.
      Risk assessment in solitary fibrous tumors: validation and refinement of a risk stratification model.
      Risk was categorized as low in 7 patients (58.3%) and intermediate in 5 (41.6%) with no patient scoring within the high risk group.
      Table 2Demicco et al. risk stratification model. Patient and tumour indices measured and recurrence risk classification displayed.
      • Cranshaw I.M.
      • Gikas P.D.
      • Fisher C.
      • Thway K.
      • Thomas J.M.
      • Hayes A.J.
      Clinical outcomes of extra-thoracic solitary fibrous tumours.
      Risk FactorScore
      Age
      <550
      >551
      Tumour size (cm)
      <50
      5 to < 101
      10 to <152
      >153
      Mitotic rate (/10 HPF)
      00
      1–31
      >/ = 42
      Tumour necrosis
      <10%0
      >/ = 10%1
      Risk classTotal score
      Low0–3
      Intermediate4–5
      High6–7
      Table 3Anatomical location of SFTs within series.
      LocationNumber of cases%
      Upper Limb216.7%
      Lower Limb541.7%
      Torso18.3%
      Pelvic433.3%
      Table 4Tumour indices of SFTs within series.
      N (%)
      Necrosis present2 (16.7%)
      Mitotic rate
       Low <4 HPF10 (83.3%)
       High >4 HPF2 (16.7%)
      Cellularity
       Low2 (16.7%)
       Moderate1 (8.3%)
       High9 (75%)
      Pleomorphism
       Low10 (83.3%)
       Moderate1 (8.3%)
       High1 (8.3%)

      4. Discussion

      In comparison to many previously published series, only extra-thoracic and extra-meningeal SFTs were included, potentially improving the relativity of these results to musculoskeletal oncologists. Importantly all diagnoses were made after 2002, and thus all tumours meet the current SFT criteria.
      • World Health Organization
      Pathology & Genetics Tumours of Soft Tissue and Bone.
      Furthermore, all patients were managed at one hospital excluding variability between surgeons of different centres, which may have occurred within larger, multicentre series.
      • Van Houdt W.J.
      • Westerveld C.M.A.
      • Vrijenhoek J.E.P.
      • et al.
      Prognosis of solitary fibrous tumors: a multicenter study.
      ,
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      A significant proportion of patients in previous series have had re-excision of the tumour due to unknown or positive margins.
      • Van Houdt W.J.
      • Westerveld C.M.A.
      • Vrijenhoek J.E.P.
      • et al.
      Prognosis of solitary fibrous tumors: a multicenter study.
      ,
      • Demicco E.G.
      • Park M.S.
      • Araujo D.M.
      • et al.
      Solitary fibrous tumor: a clinicopathological study of 110 cases and proposed risk assessment model.
      No patient in this series received neo-adjuvant or adjuvant therapy in combination with surgery with curative intent. However, this study has a relatively small sample size in comparison to other series, with multi-site series having in excess of 240 patients.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      Table 5 demonstrates a comparison of this series to other single site series.
      Table 5Summary of single site SFT series published in the literature. Outlining the number of patients, malignant status, follow up and survival data where available. NA = not available.
      StudyNumber of patientsPrimary tumour locationBenign/MalignantMedian Follow- up (months)5 year overall survival
      Spitz FR 1998
      • Spitz F.R.
      • Bouvet M.
      • Pisters P.W.T.
      • Pollock R.E.
      • Feig B.W.
      Hemangiopericytoma: a 20-year single-institution experience.
      36All sitesNA5771%
      DeVito 2015
      • DeVito N.
      • Henderson E.
      • Han G.
      • et al.
      Clinical characteristics and outcomes for solitary fibrous tumor (SFT): a single center experience.
      82Extrameningeal42/405565%
      O'Neill 2017
      • O'Neill A.C.
      • Tirumani S.H.
      • Do W.S.
      • et al.
      Metastatic patterns of solitary fibrous tumors: a single-institution experience.
      123All sites59/64124NA
      Cranshaw 2009
      • Cranshaw I.M.
      • Gikas P.D.
      • Fisher C.
      • Thway K.
      • Thomas J.M.
      • Hayes A.J.
      Clinical outcomes of extra-thoracic solitary fibrous tumours.
      33Extrathoracic15/184366%
      This series12Extrathoracic, extrameningeal11/141NA
      The heterogeneity of the series in Table 5 does make comparisons difficult. However, extrathoracic SFT disease is often noted to have more aggressive features on pathological assessment and worse disease free survival.
      • O'Neill A.C.
      • Tirumani S.H.
      • Do W.S.
      • et al.
      Metastatic patterns of solitary fibrous tumors: a single-institution experience.
      This is important for our series, which only has assessed the outcomes of extrameningeal and extrathoracic SFTs.
      All tumours were excised completely on primary procedure and no recurrences were encountered. The length of follow up was comparable to other studies, where a 18.5% recurrence rate was observed.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      ,
      • Demicco E.G.
      • Park M.S.
      • Araujo D.M.
      • et al.
      Solitary fibrous tumor: a clinicopathological study of 110 cases and proposed risk assessment model.
      Distant disease progression has been described in patients with SFT, in this series only 50% of patients underwent chest surveillance with radiographs.
      The outcome of excision of SFTs has been reviewed in several series with confliction over prognostic factors. Tumour size >10 cm and high mitotic rate were associated with a significant increase in metastatic rate in Van Houdt et al.’s series.
      • Van Houdt W.J.
      • Westerveld C.M.A.
      • Vrijenhoek J.E.P.
      • et al.
      Prognosis of solitary fibrous tumors: a multicenter study.
      However, this series included intra-thoracic SFTs. Conversely Pasquali et al. found larger tumour size to be associated with a better prognosis and reduced recurrence rate. Furthermore, Pasquali et al.’s series showed on multivariable analysis that a high mitotic rate, cellular atypia and hypercellularity were significantly associated with disease recurrence.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      These key variables were used in their recurrence risk model, Table 1.
      A further risk stratification scheme was proposed by Demicco et al., in 2012.
      • Demicco E.G.
      • Park M.S.
      • Araujo D.M.
      • et al.
      Solitary fibrous tumor: a clinicopathological study of 110 cases and proposed risk assessment model.
      This suggested that small tumour size and low mitotic rates are highly unlikely to metastasize, whereas large (>15 cm) tumours in patients >55 years of age with mitotic figures ≥4/10 high-power fields have a high risk of both metastasis and death, and require close follow up. This group then verified and refined their model, Table 2, and found that adding tumour necrosis improved the power of their model.
      • Demicco E.G.
      • Wagner M.J.
      • Maki R.G.
      • et al.
      Risk assessment in solitary fibrous tumors: validation and refinement of a risk stratification model.
      Whilst this cohort includes intra-abdominal and intra-thoracic SFTs it further suggests that follow up can be stratified by tumour characteristics.
      Using their risk recurrence model, Pasquali et al. advised upon reduced follow up scheduling and potentially non-operative management for the treatment of specific cases of SFT. Patients with low mitotic rate, cellularity and pleomorphism appeared at virtually no risk of recurrence, and thus low intensity follow up or non-operative management of unfit patients could be recommended.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      Contrastingly, high mitotic rate, cellularity and pleomorphism were features of high risk of recurrence necessitating longer term follow up. Applying this several patients within our dataset could have been discharged post-operatively or if deemed a high anaesthetic risk offered non operative management. The Pasquali recurrence model was not validated by the authors in a separate series, a noted weakness of their series, but on application to our small case series seems to be appropriate for guiding post-operative follow up reviews. Surprisingly Demicco et al.’s recurrence risk model did not identify any patients within this dataset as high risk.
      • Demicco E.G.
      • Wagner M.J.
      • Maki R.G.
      • et al.
      Risk assessment in solitary fibrous tumors: validation and refinement of a risk stratification model.
      Given that no tumour recurrence locally or distant was observed, it could be debated that surveillance with chest radiographs was over used. 6 patients received chest radiographs on follow up review, however only 2 patients were identified as high risk upon using both the Pasquali and Demicco recurrence risk models.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      ,
      • Demicco E.G.
      • Wagner M.J.
      • Maki R.G.
      • et al.
      Risk assessment in solitary fibrous tumors: validation and refinement of a risk stratification model.
      The presence of necrosis within a soft tissue sarcoma is an important predictor of disease aggressiveness, and it is utilised in the Trojani grading system.
      • Trojani M.
      • Contesso G.
      • Coindre J.M.
      • et al.
      Soft-tissue sarcomas of adults; study of pathological prognostic variables and definition of a histopathological grading system.
      However, in SFTs the presence of necrosis and its prognostic significance is contentious.
      • Van Houdt W.J.
      • Westerveld C.M.A.
      • Vrijenhoek J.E.P.
      • et al.
      Prognosis of solitary fibrous tumors: a multicenter study.
      ,
      • Gold J.S.
      • Antonescu C.R.
      • Hajdu C.
      • et al.
      Clinicopathologic correlates of solitary fibrous tumors.
      Necrosis was not seen to be predictive of disease progression in the largest known case series, with the caveat that a significant proportion of patients had received neo-adjuvant therapy, which may have induced tumour modification.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      The presence of necrosis has been included in Demicco et al.’s risk recurrence model, however their series includes SFTs of all anatomical locations.
      • Demicco E.G.
      • Wagner M.J.
      • Maki R.G.
      • et al.
      Risk assessment in solitary fibrous tumors: validation and refinement of a risk stratification model.
      In a large case series of 92 patients with extrathoracic SFTs, by Vallat-Decouvelaere et al., necrosis was associated with, but not predictive, of aggressive clinical behaviour.
      • Vallat-Decouvelaere A.V.
      • Dry S.M.
      • Fletcher C.D.M.
      Atypical and malignant solitary fibrous tumors in extrathoracic locations: evidence of their comparability to intra-thoracic tumors.
      Due to the persistence of uncertainty over the importance of the presence of significant necrosis within SFTs, it appears prudent to continue to include it as a potential marker of poor clinical outcome.
      The recurrent gene fusion NAB2-STAT6 is believed to be the driver of the disease, and importantly, subgroups of different NAB2-STAT6 fusion types have been recognised. These subgroups have differing prognoses, with the NAB2ex6-STAT6ex16/17 occurring in deep soft tissues of younger patients and displaying more aggressive behaviour and NAB2ex4-STAT6ex2/3 corresponding to the more benign pleural based disease.
      • Barthelmeß S.
      • Geddert H.
      • Boltze C.
      • et al.
      Solitary fibrous tumors/hemangiopericytomas with different variants of the NAB2-STAT6 gene fusion are characterized by specific histomorphology and distinct clinicopathological features.
      An important future step in the management of this disease will be when genetic investigations are integrated in to clinical diagnosis and management.
      Surgical excision remains the primary treatment modality. Due to the vascular nature of these tumours the significance of antiangiogenic therapies has been investigated. Drugs such as sorafenib and sunitinib, have been used, and shown to be active in patients with locally advanced or metastatic disease.
      • Stacchiotti S.
      • Negri T.
      • Libertini M.
      • et al.
      Sunitinib malate in solitary fibrous tumor (SFT).
      Novel targeted therapies to growth signalling pathways, such as Pazopanib have been trialled in patients with metastatic disease, with similar overall survival results noted in comparison to previously reported series.
      • Maruzzo M.
      • Martin-Liberal J.
      • Messiou C.
      • et al.
      Pazopanib as first line treatment for solitary fibrous tumours: the Royal Marsden Hospital experience.
      The NAB2-STAT6 fusion leads to alteration in growth and development and an overexpression of growth factors, receptor tyrosine kinases and histone deacetylases. It is hoped that these pathways may be therapeutic targets for future therapies. Thermoablation techniques for the treatment of extremity SFTs, such as microwave ablation and high intensity focused ultrasound, have yet to be reported in the literature, however a recent case study by Fiore et al. demonstrated effective treatment of a recurrent pleural SFT via microwave ablation, suggestive that this may be an increasingly investigated technique.
      • Fiore F.
      • Stoia V.
      • Somma F.
      Surgical Recurrence of Solitary Fibrous Tumor of the Pleura Treated with Microwave (MW) Thermoablation: A Case Report.
      Following this review of our case series and utilising risk recurrence models published in the literature we have changed our follow up protocol. For new patients we will apply the Pasquali model, but also add the presence or absence of necrosis as an additional risk factor to consider.
      • Pasquali S.
      • Gronchi A.
      • Strauss D.
      • et al.
      Resectable extra-pleural and extra-meningeal solitary fibrous tumours: a multi-centre prognostic study.
      Follow up reviews with chest radiographs will be reserved for patients with SFTs which had malignant features on pathological assessment, or who are deemed high risk utilising the Pasquali recurrence model.
      Tabled 1Key learning points
      • Complete surgical excision remains the mainstay of treatment
      • Adjuvant therapy remains important for incomplete or unresectable tumours and metastatic disease
      • Systemic targeted therapies are required
      • Management of SFTs may become stratified to NAB2-STAT6 fusion types

      Declaration of competing interest

      Each author certifies that he or she has no commercial associations (e.g. consultancies, stock ownership, equity interest, patent/licensing arrangements) that might pose a conflict of interest in connection with the submitted article. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institution and/or national research committee and with the 1964 Helsinki declaration and it's later amendments or comparable ethical standards. This research was performed at Glasgow Royal Infirmary and the Queen Elizabeth University Hospital.

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