Effectiveness of Classification and Scoring Systems in Solitary Fibrous Tumor Prognosis Prediction

Effectiveness of Classification and Scoring Systems in Solitary Fibrous Tumor Prognosis Prediction | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effectiveness of Classification and Scoring Systems in Solitary Fibrous Tumor Prognosis Prediction Hüseyin Fatih Sezer, Aykut Eliçora, Salih Topçu, Büşra Yaprak Bayrak This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7552318/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objectives Because thoracic solitary fibrous tumors (SFTs) are rare, there is limited information on their clinical features, treatment, and follow-up. The literature mainly comprises individual case reports. Definitions, classifications, and scoring systems have been created to predict their clinical behaviour. Our study aimed to analyse SFT data to identify prognosis-related factors and to compare the performance of two describing approaches and three risk stratification models. Methods Medical data from 37 patients, including 32 patients with SFT aged 18 years and older who underwent surgical treatment and five patients diagnosed by biopsy between 2004 and 2024, were analysed retrospectively. Parameters affecting recurrence and survival were investigated, and the effectiveness of existing classification and scoring systems was compared. Results Factors potentially associated with recurrence included four or more mitoses (10 HPF) (p = 0.023), necrosis (p = 0.007), at least 10% Ki-67 positivity (p = 0.012), malignancy (p = 0.046), and tumor size (p = 0.022). Relapses were observed only in the malignant group according to the England classification (p = 0.046), only in stage 3 according to the de Perrot classification (p = 0.161), only in those with scores of three or higher according to the Tapias classification (p = 0.036), only in those with scores of two or higher according to the Diebold classification (p = 0.021), and all in high-stage groups (p = 0.001) according to the Demicco classification. All recurrences occurred at significant or high scores. Conclusions The factors directly affecting prognosis include malignancy, a mitotic count of 4 (10 HPF) or higher, necrosis, recurrence, and ki-67 ≥ 10%, while indirectly influencing prognosis are increasing age, increasing size, and pleomorphism. For malignancy criteria, England's standards should be used, and de Perrot's classification is partly helpful. The Tapias, Diebold, and Demicco scoring systems are highly effective in predicting recurrence and prognosis. However, the modified Demicco system is more advantageous and offers a higher level of assessment. Cardiothoracic Surgery Solitary Fibrous Tumor England criteria de Perrot classification Tapias score Diebold score Demicco score Figures Figure 1 Figure 2 Figure 3 Figure 4 INTRODUCTION Thoracic solitary fibrous tumors (SFTs) are rare, and their usual location is the pleura. 1 – 4 Until 2005, 800–900 cases were reported in the literature, and today, around 1000 cases are documented. 2 , 5 , 6 , 7 Its incidence has been reported as 2.8/100000. 2,8 The exact aetiology is unknown. 7 , 9 , 10 It was previously regarded as a form of mesothelioma, but later, it was recognised as a distinct entity tumor. 2 , 5 , 11 These processes have led to confusion concerning clinical and pathological aspects issues. 12 Furthermore, because tumors are rare, information about their clinical presentation, treatment, and follow-up procedures is limited. The literature generally consists of individual case reports. In fact, there are few studies that include the results of more than 50 patients who were surgically treated, and these are usually multicentre. Although they generally have a good prognosis, a small percentage (10–30%) may demonstrate malignant behaviour. It is clinically important to predict which ones might display malignancy behaviour. 5 , 12 , 13 To understand this situation, various definitions, classifications, and scoring systems have been established over time. 3 England defined malignancy criteria based on histopathology, and de Perrot believed that histopathology alone could not reflect prognosis, incorporating morphological appearance into their criteria alongside histological factors features. 5 , 13 , 14 Later, Tapias, Diebold, and Demicco introduced prognosis prediction using their own scoring systems. These classification and scoring systems were developed based on data from a small number of patients. Several studies are now examining the effectiveness of these approaches. In these studies, classification or scoring systems were generally compared in pairs, but a study in which all of them were compared or their results were analysed has not yet been presented. In our study, we aimed to compare the effectiveness of all existing classifications and scoring systems related to this disease, for which limited clinical information is available, using our long-term results, and to identify the factors that may influence a poor prognosis. METHODS Medical data from 37 patients, including 32 patients with SFTs aged 18 years and older who underwent surgical treatment and five patients diagnosed via biopsy between 2004 and 2024 at Kocaeli University Thoracic Surgery Clinic, were analysed retrospectively. Seven patients who had surgery were excluded due to incomplete follow-up data, resulting in a final sample of 30 patients. Written and verbal informed consent was obtained from all patients. Ethical approval was granted by the Kocaeli University Ethics Committee. Data were accessed for research purposes from 12.03.2024 for a period of three months. Patient data were anonymised and accessed through hospital information systems, imaging systems, outpatient clinic follow-up records, and telephone calls. Follow-up, survival, mortality, recurrence, and metastasis durations were calculated using the date of diagnosis or the date of surgery as references. Postoperative mortality was defined as deaths within the first month after the operation. Patient data were anonymised, and demographic characteristics, tumor details, comorbidity information, clinical features, pathological data (including histological, morphological, and immunological aspects), radiological findings, preoperative, intraoperative, and postoperative outcomes, non-surgical treatments, recurrence, metastasis, overall survival (OS), disease-free survival (DFS), follow-up data, and long-term outcomes were analysed. The patient’s history was reviewed prior to the operation. Physical examination, routine blood tests, pulmonary function tests, and cardiac and respiratory assessments were performed. Radiological examinations, including X-ray and CT scans, were carried out on all patients, and nuclear medicine PET-CT (FDG) was performed on some. Preoperative diagnosis was confirmed through CT-guided tru-cut biopsy in certain cases. Patients who could not be diagnosed beforehand were diagnosed during surgery. The procedures included posterolateral thoracotomy or video-assisted thoracoscopic surgery (VATS). Early follow-up occurred in the outpatient clinic at the 1st, 3rd, and 7th weeks after discharge. Chemotherapy (KT) and radiotherapy (RT) were administered to patients with microscopic residual disease or recurrence, with closer follow-up in collaboration with the oncology department. Long-term follow-up was conducted every 6 months for the first 2 years, then annually thereafter. The malignant criteria for SFTs were established by England et al. 14 . A classification that includes both morphological and histological features was created by De Perrot. 5 De Perrot et al. classified SFTs as 1- benign tumor with pedicle, 2- benign tumor with broad base, 3- malignant tumor with pedicle, and 4- malignant tumor with broad base. 5 In our study, benign versus malignant differentiation was made according to England's and de Perrot's criteria 5,14 , and recurrence risk was estimated based on Tapias 15 , Diebold 16 , and Demicco's 2017 17 scoring systems. (Table 1) Statistical analysis All statistical analyses were performed using IBM SPSS for Windows version 29.0 (IBM Corp., Armonk, NY, USA). Shapiro-Wilk's test was used to assess the normality assumption. Continuous variables were presented with mean±standard deviation or median and interquartile range (IQR). Categorical variables were summarized as counts and percentages. Comparisons between groups were performed using Mann-Whitney U test since the normality assumption did not hold. Associations between categorical variables were examined using the Chi-square test. Kaplan-Meier method with the log-rank test was used for the survival analysis. A p-value<0.05 was considered statistically significant. RESULTS The mean age was 59.40±13.23 years. The gender distribution was 16 (53.3%) males and 14 (46.7%) females. 20 (66.7%) patients had a smoking history. Pleural effusion was observed in 6 (20%) patients, all of whom belonged to the malignant group. Preoperative diagnosis was established by percutaneous biopsies in 19 (63.33%) patients. Isolated mass excision was performed in 21 (84%) patients, whereas lung parenchyma was also removed with wedge resection along with the mass in 4 (16%) patients. Incomplete resection was performed in 2 (8%) patients. Older age (p=0.001), smoking (p=0.03), and pleural effusion (p=0.038) were significantly more common in the malignant group (Table 2). 13 (52%) tumors originated from the parietal pleura and 12 (48%) from the visceral pleura. The median tumor size was 8.75 cm. Tumor morphology showed that 6 (24%) tumors were pedunculated and 19 (76%) were sessile. Mitosis of 4 or more (10 HPF) was observed in 5 (16.7%) patients, necrosis in 16 (53.3%) patients, high cellularity in 6 (24%) patients, and pleomorphism in 4 (13.3%) patients. CD 34 positivity was seen in 27 (90%) patients, bcl-2 positivity in 29 (96.7%) patients, STAT 6 positivity in 9 (90%) patients, and Ki-67 of 10% or more was found in 12 (40%) patients. Although tumor size was numerically larger in the malignant group, this difference was not statistically significant (p=0.150). Pleomorphism was observed only in the malignant group, but it was not statistically significant (p=0.056). Tumors with sessile morphology predominated in the malignant group (p=0.032). The STAT 6 marker, which was introduced into routine practice after a certain date, was used in 10 patients. Its sensitivity for solitary tumors was high at 90%, but it was not significant in differentiating benign from malignant lesions (p=0.840). When pathological markers and immunohistochemistry were evaluated, only mitosis, necrosis, and high cellularity showed significantly higher incidence in the malignant group (p=0.046, p=0.001, and p=0.038, respectively). (Table 3) Follow-up was 50±24.01 months. Recurrence was noted in 5 (16.7%) patients, and metastasis to the contralateral lung occurred in 1 (4.76%) patient. Chemotherapy was given to 4 (13.3%) patients, while radiotherapy was administered to 6 (20%) patients, all within the malignant group. All recurrences and metastases to the contralateral lung occurred exclusively in the malignant group (p=0.046). During follow-up, a total of 11 (36.7%) patients died. Of these, 10 (11.11%) were from the malignant group (p=0.032), with only one mortality in the benign group, which was a surgical death within the first 30 days. Two (9.52%) of the deaths in the malignant group were related to the disease (SFT). (Table 4) The median time to recurrence was 36 (22-58) months. Recurrence was observed only in the necrosis, 10%≤ Ki-67 positive, and malignant groups (p=0.007, p=0.012, p=0.046, respectively). Recurrence occurred in 3 patients with four or more mitoses (10 HPF) (p=0.023) and in 2 patients with pleomorphism (p=0.23). (Table 5) In the multivariate analysis involving significant parameters, only malignancy remained significant. The median age was higher in the recurrence group (65 vs. 57) (p=0.481). Among the demographic and morphological features in the recurrence group, only size was significant, being larger in the malignant group (16 cm vs. 6 cm) (p=0.022). Expected Overall Survival (OS) was 68.58±5.67 months, and although a numerical difference was observed, there was no statistically significant difference between the benign and malignant groups (p=0.15). Expected Disease-Free Survival (DFS) was 78.72±4.89 months, and despite a numerical difference, there was no statistically significant difference between the benign and malignant groups (p=0.107). (Figures 1-4), (Table 6) Relapses were observed only in the malignant group according to the England classification (p=0.046), only in stage 3 according to the de Perrot classification (p=0.161), only in patients with scores of three or higher according to the Tapias classification (p=0.036), only in those with scores of two or higher according to the Diebold classification (p=0.021), and all occurred in high-stage cases (p=0.001) according to the Demicco classification. All relapses were associated with significant or high scores. (Table 7) Due to the low number of recurrences, multi-variable analysis could not be performed to compare the classifications. DISCUSSION Most SFTs present as benign behaviour. 5 , 6 However, there have also been cases of benign to malignant transformation reported. 5 Therefore, predicting tumors that may exhibit malignant behaviour is important in clinical practice. There are few studies in the literature on SFTs, including results from 50 or more patients who have undergone surgery, and these are generally multicentre. Consequently, more case series are needed to better analyse disease behaviour, follow-up, and treatment approaches. Our study aimed to identify factors affecting prognosis by analysing data on SFTs and to compare the performance of two grouping methods and three risk classification models proposed in the literature regarding prognosis and long-term follow-up results. The reported rate of malignancy in SFTs is 12–37%. 1,5,18 Benign to malignant conversion has been reported in cases and is associated with size. 5 , 19 , 20 Malignant tumors are expected to be larger, more symptomatic, atypically localised, younger in age, sessile, and multifocal. 1 , 4 , 6 , 7 , 20 – 24 In our study, age was significantly higher in malignant patients (65 − 42) (p = 0.001). Tumor size was numerically larger in malignant patients (11 − 8.5 cm) (p = 0.150), and most of those with ki-67 (10% and above) + were in the malignant group (p = 0.371). Recurrences are observed more often in the first two to three years. 1 , 2 , 23 Recurrence rates range from 0 to 17% in benign cases and from 13.6 to 66.7% in malignant ones cases. 2 , 3 , 6 , 13 , 15 , 16 , 20 , 22 , 24 – 26 Sesile morphological type, resections larger than the wedge, and CD34 negativity are significant indicators of malignancy recurrence. 23 , 24 In our study cohort, 16.7% of recurrences occurred in patients with malignancies, with a median recurrence time of 36 months. Although no recurrence was observed in patients without mitosis, recurrences were seen in 3 patients with a mitosis count of 4 (10 HPF) or more and in 2 patients with a mitosis count of 4 (10 HPF) (p = 0.023). Recurrences were only recorded in patients with necrosis (p = 0.007), malignancy (p = 0.046), and larger tumor size (p = 0.022). Recurrence was more significant (p = 0.012) in patients with ki-67 positivity ≥ 10%. Although the mean age of patients with recurrence was higher (65 vs. 57), the difference was not statistically significant (p = 0.481). However, since malignancy is a major factor in recurrence and the mean age of malignant patients was higher (p = 0.001), age has an indirect significance regarding recurrence. No correlation was found between pleomorphism and recurrence (p = 0.230). Nonetheless, it was hypothesised that a significant correlation might exist because of the increase in cases, as these were observed exclusively in the malignant group. Malignancy factors include originating from the parietal pleura or chest wall, isolated resection, malignant pleural effusion, large size (10 cm), mitotic number > 10 (10 HPF), and a high proliferation rate. 6 , 8 , 13 The 5- and 10-year DFS rates are reported to be 82–95% and 67-90.8%, respectively, and this rate is 58-72.1–60.5% in the malignant group, and 95.7–100% in the benign group (5 years only). 4 , 6 , 8 , 13 , 15 , 21 , 23 In our study, DFS was 96.4% at 2 years, 74.2% at 5 years, and 74.2% at 10 years. Since there was no recurrence in the benign group, it was 100%, while in the malignant group, it was 95% at 2 years, 61.8% at 5 years, and 61.8% at 10 years (p = 0.107). Our findings show DFS rates align with the literature. There was a numerical difference between the benign and malignant groups, and we expect a statistically significant difference as the number of cases increases. Studies have reported 5- and 10-year survival rates of 86–94% and 72.1–77%, respectively, with a median survival of 14–24 years. 3 , 9 , 10 , 15 , 21 , 23 In benign SFT cases, 5-year survival rates are 89–100%; in malignant cases, 5-year survival rates range from 45.5–89%, and 10-year survival rates are 66.9%. 3,6,21–23,26 We attribute the numerical differences between the results of the studies to variations in the number of malignant patients and surgeries. In our study, OS was 90% at 2 years, 67.7% at 5 years, and 51.6% at 10 years. OS in the benign group was 88.89% at all follow-up time points, whereas OS in the malignant group was 90.5% at 2 years, 59.9% at 5 years, and 37.4% at 10 years. The number of patients with malignancies was significantly higher in our patient population. Therefore, although our OS rate was slightly lower for all patients compared with that in the literature, the rate in patients with malignancies was comparable. The expected OS was 80.11 months in benign patients and 64.01 months in malignant cases (p = 0.15). We believe that the statistical difference between the two groups will become more evident as the number of cases increases. In the study by Tan et al. 24 , OS was 76% and DFS was 53% in malignant patients. When the survival graph from this study is analysed, it is observed that both rates are nearly equal during the first 2 years, with the disparity emerging after the 3rd year and then progressing in tandem with these rates. Similarly, in our study of malignant tumors, the difference widened after the 2nd year. Factors affecting prognosis have been reported to include incomplete resection, recurrence, large size (10 cm), and pedicled genetic molecular factors encapsulated. 4 , 6 , 15 , 16 , 22 , 24 , 27 On the other hand, some authors have reported that tumor size, the pleura from which the tumor originates, or being symptomatic are not effective in prognosis. 5 , 6 , 8 , 13 The most important prognostic factor related to surgical treatment is complete blockage removal resection. 18 In the study by Lahon et al. 23 , which included multifactorial analysis, it was found that factors related to short-term survival in malignant tumors were vena cava compression, multifocality, resections larger than wedge, and recurrence, with recurrence being the most significant factor. In our study, the factors directly influencing prognosis were recurrence, malignancy, ki-67 > 10%, mitotic count of 4 (10 HPF) or more, necrosis; while the indirect factors were age, tumor size, and pleomorphism. Due to numerical limitations, we could not compare these factors through multifactorial analysis; however, the most impactful factor was recurrence based on individual assessments. Surgery and chemoradiotherapy are employed in treating SFT. The timing of radiotherapy remains a contentious issue. Haas et al. 28 demonstrated that surgery combined with radiotherapy offers no significant advantage in overall survival (OS), although they recommend it for tumors with poor resection margins or high mitotic activity. Radiotherapy can influence surgical outcomes and potentially increase complication rates due to its effects on tissue. In our view, radiotherapy is a viable option following R1 resections, in cases of unresectable tumors, or with metastases. Since anatomical classification systems cannot be used effectively, specialised classifications that are not based on large patient groups are employed to assess prognosis and recurrence. 3 The low incidence of SFT may be the reason. Apart from the definitions of malignancy, the authors developed their own scoring systems beyond malignancy criteria, incorporating factors that may influence prognosis and recurrence. They occasionally compared their scoring systems with others. New scoring studies are ongoing progress. 13 , 16 While some authors have reported that isolated histological or morphological features can be useful for prediction, others have found that these alone are not enough. For example, in a study by Tan et al., recurrence rates were reported as 2%, 8%, 14%, and 63% according to Perrot's classification. 24 However, Tapias et al. found no significant difference in these parameters when comparing high- and low-risk groups according to Perrot and England's scoring. 15 In this study, the performance of these definitions, classifications, and systems was compared. All recurrences were observed in England's malignant group (p = 0.046), de Perrot stage 3 (p = 0.161), Tapias' cases with a total score of 3 and above (p = 0.036), Diebold's cases with a total score of 2 and above (p = 0.021), Demicco's stage 3 (p = 0.001). 5,14,15,16,17 Based on these results, it was observed that England's criteria should be used for malignancy, de Perrot's classification was partially effective, and the Tapias, Diebold, and Demicco scoring systems were very successful in predicting recurrence. Given our current number of cases, we consider it premature to present a statistical comparison of the superiority of any one scoring system. We plan to include this analysis in future studies with a larger sample size. However, if we must comment, the modified Demicco classification was considered to be slightly superior to the other scoring systems because it assesses more variables, creates more groupings, and most of the recurrences in our study occurred in the highest scoring stage. The weaknesses of our study included its retrospective, single-centre design and relatively small number of cases. We faced the challenge of studying a rare tumor, which prevented us from detecting a statistical difference in some instances where there was a numerical difference. Nevertheless, we gathered valuable data by comparing the effectiveness of all classifications used to predict SFT prognosis and behaviour. As a result, the factors directly affecting prognosis are malignancy, a mitotic count of 4 (10 HPF) or more, necrosis, recurrence, and ki-67 ≥ 10%, while the factors indirectly influencing prognosis include increasing age, enlarging size, and pleomorphism. 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PMID: 32315454; PMCID: PMC7318349 Tables Table 1 to 7 are available in the Supplementary Files section. Additional Declarations The authors declare no competing interests. Supplementary Files Tables.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7552318","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":511233517,"identity":"813a32af-1c9f-4edd-840c-bb15319d94e3","order_by":0,"name":"Hüseyin Fatih Sezer","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxUlEQVRIiWNgGAWjYBACA+YDDMwMNgxyIM6BB0RpYUsAakljMAZrSSBFS2IDiEeUFnM29gfMBQl16fPDDj8E2mInp9tAQItlG48B84yEw7kbb6cZALUkG5sdIOSw+z0MzLw/DuRunJ0A0nIgcRtBLceADuMBOsxwdvoHYrUAw5kngTlBXjqHaFt4DA7zJBw23CCdU3AgwYAYvxxjf/gY6DB5+dnpmz98qLCTI6gFBMBqDCAkEcrhQL6BFNWjYBSMglEwogAA4iJDp/WNLOYAAAAASUVORK5CYII=","orcid":"","institution":"Kocaeli University","correspondingAuthor":true,"prefix":"","firstName":"Hüseyin","middleName":"Fatih","lastName":"Sezer","suffix":""},{"id":511233518,"identity":"63495078-4c75-4b1f-b3f9-b6cdc1501917","order_by":1,"name":"Aykut Eliçora","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Aykut","middleName":"","lastName":"Eliçora","suffix":""},{"id":511233519,"identity":"985f9f19-6259-46e4-9b8d-426d1c7d9a79","order_by":2,"name":"Salih Topçu","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Salih","middleName":"","lastName":"Topçu","suffix":""},{"id":511233724,"identity":"e082b426-65bb-495a-96fe-66c25c1b23f2","order_by":3,"name":"Büşra Yaprak Bayrak","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Büşra","middleName":"Yaprak","lastName":"Bayrak","suffix":""}],"badges":[],"createdAt":"2025-09-06 17:11:07","currentVersionCode":1,"declarations":{"humanSubjects":true,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":true,"humanSubjectConsent":true,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-7552318/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7552318/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":90914226,"identity":"0be7d6f1-9910-44ae-9e2f-153ed50f8d7e","added_by":"auto","created_at":"2025-09-09 14:00:42","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":111214,"visible":true,"origin":"","legend":"\u003cp\u003eOver all survival (all patients)\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7552318/v1/d5eea1315d5a5754ca481dc6.jpeg"},{"id":90914227,"identity":"2c7580e9-66fa-4b6c-987f-90803b1f6079","added_by":"auto","created_at":"2025-09-09 14:00:42","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":206332,"visible":true,"origin":"","legend":"\u003cp\u003eDisease free survival (all patients)\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7552318/v1/8c6d5e1a0867a4a0a7dabc5d.jpeg"},{"id":90911952,"identity":"e4330fdc-6c42-4b58-8dfa-48d510e7f650","added_by":"auto","created_at":"2025-09-09 13:44:42","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":136649,"visible":true,"origin":"","legend":"\u003cp\u003eOver all survival (benign and malign patients)\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7552318/v1/3f2da2fdfedfbb01c37d6689.jpeg"},{"id":90914228,"identity":"20227dda-711e-4448-900c-f7beeab69e1e","added_by":"auto","created_at":"2025-09-09 14:00:42","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":222444,"visible":true,"origin":"","legend":"\u003cp\u003eDisease free survival (benign and malign patients)\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7552318/v1/cdc6a489f016a55df73a21bd.jpeg"},{"id":90914229,"identity":"eea527f3-17c9-4ea8-98f1-8039b3523014","added_by":"auto","created_at":"2025-09-09 14:00:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1063088,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7552318/v1/d4d8e03e-f43d-4e39-a43f-a74850cb9877.pdf"},{"id":90912739,"identity":"ef41ac9e-87bb-4111-b60a-95be014bd51c","added_by":"auto","created_at":"2025-09-09 13:52:42","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":39870,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-7552318/v1/96f74911b892f27fb9f86038.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eEffectiveness of Classification and Scoring Systems in Solitary Fibrous Tumor Prognosis Prediction\u003c/p\u003e","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThoracic solitary fibrous tumors (SFTs) are rare, and their usual location is the pleura.\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e Until 2005, 800\u0026ndash;900 cases were reported in the literature, and today, around 1000 cases are documented. \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e Its incidence has been reported as 2.8/100000.\u003csup\u003e2,8\u003c/sup\u003e The exact aetiology is unknown.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e It was previously regarded as a form of mesothelioma, but later, it was recognised as a distinct entity tumor.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e These processes have led to confusion concerning clinical and pathological aspects issues.\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e Furthermore, because tumors are rare, information about their clinical presentation, treatment, and follow-up procedures is limited. The literature generally consists of individual case reports. In fact, there are few studies that include the results of more than 50 patients who were surgically treated, and these are usually multicentre.\u003c/p\u003e\u003cp\u003eAlthough they generally have a good prognosis, a small percentage (10\u0026ndash;30%) may demonstrate malignant behaviour. It is clinically important to predict which ones might display malignancy behaviour.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e To understand this situation, various definitions, classifications, and scoring systems have been established over time.\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e England defined malignancy criteria based on histopathology, and de Perrot believed that histopathology alone could not reflect prognosis, incorporating morphological appearance into their criteria alongside histological factors features.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e Later, Tapias, Diebold, and Demicco introduced prognosis prediction using their own scoring systems. These classification and scoring systems were developed based on data from a small number of patients. Several studies are now examining the effectiveness of these approaches. In these studies, classification or scoring systems were generally compared in pairs, but a study in which all of them were compared or their results were analysed has not yet been presented.\u003c/p\u003e\u003cp\u003eIn our study, we aimed to compare the effectiveness of all existing classifications and scoring systems related to this disease, for which limited clinical information is available, using our long-term results, and to identify the factors that may influence a poor prognosis.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cp\u003eMedical data from 37 patients, including 32 patients with SFTs aged 18 years and older who underwent surgical treatment and five patients diagnosed via biopsy between 2004 and 2024 at Kocaeli University Thoracic Surgery Clinic, were analysed retrospectively. Seven patients who had surgery were excluded due to incomplete follow-up data, resulting in a final sample of 30 patients. Written and verbal informed consent was obtained from all patients. Ethical approval was granted by the Kocaeli University Ethics Committee. Data were accessed for research purposes from 12.03.2024 for a period of three months.\u003c/p\u003e\n\u003cp\u003ePatient data were anonymised and accessed through hospital information systems, imaging systems, outpatient clinic follow-up records, and telephone calls. Follow-up, survival, mortality, recurrence, and metastasis durations were calculated using the date of diagnosis or the date of surgery as references. Postoperative mortality was defined as deaths within the first month after the operation.\u003c/p\u003e\n\u003cp\u003ePatient data were anonymised, and demographic characteristics, tumor details, comorbidity information, clinical features, pathological data (including histological, morphological, and immunological aspects), radiological findings, preoperative, intraoperative, and postoperative outcomes, non-surgical treatments, recurrence, metastasis, overall survival (OS), disease-free survival (DFS), follow-up data, and long-term outcomes were analysed. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe patient\u0026rsquo;s history was reviewed prior to the operation. Physical examination, routine blood tests, pulmonary function tests, and cardiac and respiratory assessments were performed. Radiological examinations, including X-ray and CT scans, were carried out on all patients, and nuclear medicine PET-CT (FDG) was performed on some. Preoperative diagnosis was confirmed through CT-guided tru-cut biopsy in certain cases. Patients who could not be diagnosed beforehand were diagnosed during surgery. The procedures included posterolateral thoracotomy or video-assisted thoracoscopic surgery (VATS). Early follow-up occurred in the outpatient clinic at the 1st, 3rd, and 7th weeks after discharge. Chemotherapy (KT) and radiotherapy (RT) were administered to patients with microscopic residual disease or recurrence, with closer follow-up in collaboration with the oncology department. Long-term follow-up was conducted every 6 months for the first 2 years, then annually thereafter.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe malignant criteria for SFTs were established by England et al.\u003csup\u003e14\u003c/sup\u003e. A classification that includes both morphological and histological features was created by De Perrot.\u003csup\u003e5\u003c/sup\u003e De Perrot et al. classified SFTs as 1- benign tumor with pedicle, 2- benign tumor with broad base, 3- malignant tumor with pedicle, and 4- malignant tumor with broad base.\u003csup\u003e5\u003c/sup\u003e In our study, benign versus malignant differentiation was made according to England\u0026apos;s and de Perrot\u0026apos;s criteria\u003csup\u003e5,14\u003c/sup\u003e, and recurrence risk was estimated based on Tapias\u003csup\u003e15\u003c/sup\u003e, Diebold\u003csup\u003e16\u003c/sup\u003e, and Demicco\u0026apos;s 2017\u003csup\u003e17\u003c/sup\u003e scoring systems. (Table 1)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical analysis\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll statistical analyses were performed using IBM SPSS for Windows version 29.0 (IBM Corp., Armonk, NY, USA). Shapiro-Wilk\u0026apos;s test was used to assess the normality assumption. \u0026nbsp;Continuous variables were presented with mean\u0026plusmn;standard deviation or median and interquartile range (IQR). \u0026nbsp;Categorical variables were summarized as counts and percentages. \u0026nbsp;Comparisons between groups were performed using Mann-Whitney U test since the normality assumption did not hold. Associations between categorical variables were examined using the Chi-square test. \u0026nbsp;Kaplan-Meier method with the log-rank test was used for the survival analysis. \u0026nbsp;A p-value\u0026lt;0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003eThe mean age was 59.40\u0026plusmn;13.23 years. The gender distribution was 16 (53.3%) males and 14 (46.7%) females. 20 (66.7%) patients had a smoking history. Pleural effusion was observed in 6 (20%) patients, all of whom belonged to the malignant group. Preoperative diagnosis was established by percutaneous biopsies in 19 (63.33%) patients. Isolated mass excision was performed in 21 (84%) patients, whereas lung parenchyma was also removed with wedge resection along with the mass in 4 (16%) patients. Incomplete resection was performed in 2 (8%) patients. Older age (p=0.001), smoking (p=0.03), and pleural effusion (p=0.038) were significantly more common in the malignant group (Table 2).\u003c/p\u003e\n\u003cp\u003e13 (52%) tumors originated from the parietal pleura and 12 (48%) from the visceral pleura. The median tumor size was 8.75 cm. Tumor morphology showed that 6 (24%) tumors were pedunculated and 19 (76%) were sessile. Mitosis of 4 or more (10 HPF) was observed in 5 (16.7%) patients, necrosis in 16 (53.3%) patients, high cellularity in 6 (24%) patients, and pleomorphism in 4 (13.3%) patients. CD 34 positivity was seen in 27 (90%) patients, bcl-2 positivity in 29 (96.7%) patients, STAT 6 positivity in 9 (90%) patients, and Ki-67 of 10% or more was found in 12 (40%) patients. Although tumor size was numerically larger in the malignant group, this difference was not statistically significant (p=0.150). Pleomorphism was observed only in the malignant group, but it was not statistically significant (p=0.056). Tumors with sessile morphology predominated in the malignant group (p=0.032). The STAT 6 marker, which was introduced into routine practice after a certain date, was used in 10 patients. Its sensitivity for solitary tumors was high at 90%, but it was not significant in differentiating benign from malignant lesions (p=0.840). When pathological markers and immunohistochemistry were evaluated, only mitosis, necrosis, and high cellularity showed significantly higher incidence in the malignant group (p=0.046, p=0.001, and p=0.038, respectively). (Table 3)\u003c/p\u003e\n\u003cp\u003eFollow-up was 50\u0026plusmn;24.01 months. Recurrence was noted in 5 (16.7%) patients, and metastasis to the contralateral lung occurred in 1 (4.76%) patient. Chemotherapy was given to 4 (13.3%) patients, while radiotherapy was administered to 6 (20%) patients, all within the malignant group. All recurrences and metastases to the contralateral lung occurred exclusively in the malignant group (p=0.046). During follow-up, a total of 11 (36.7%) patients died. Of these, 10 (11.11%) were from the malignant group (p=0.032), with only one mortality in the benign group, which was a surgical death within the first 30 days. Two (9.52%) of the deaths in the malignant group were related to the disease (SFT). (Table 4)\u003c/p\u003e\n\u003cp\u003eThe median time to recurrence was 36 (22-58) months. Recurrence was observed only in the necrosis, 10%\u0026le; Ki-67 positive, and malignant groups (p=0.007, p=0.012, p=0.046, respectively). Recurrence occurred in 3 patients with four or more mitoses (10 HPF) (p=0.023) and in 2 patients with pleomorphism (p=0.23). (Table 5) In the multivariate analysis involving significant parameters, only malignancy remained significant. The median age was higher in the recurrence group (65 vs. 57) (p=0.481). Among the demographic and morphological features in the recurrence group, only size was significant, being larger in the malignant group (16 cm vs. 6 cm) (p=0.022).\u003c/p\u003e\n\u003cp\u003eExpected Overall Survival (OS) was 68.58\u0026plusmn;5.67 months, and although a numerical difference was observed, there was no statistically significant difference between the benign and malignant groups (p=0.15). Expected Disease-Free Survival (DFS) was 78.72\u0026plusmn;4.89 months, and despite a numerical difference, there was no statistically significant difference between the benign and malignant groups (p=0.107). (Figures 1-4), (Table 6)\u003c/p\u003e\n\u003cp\u003eRelapses were observed only in the malignant group according to the England classification (p=0.046), only in stage 3 according to the de Perrot classification (p=0.161), only in patients with scores of three or higher according to the Tapias classification (p=0.036), only in those with scores of two or higher according to the Diebold classification (p=0.021), and all occurred in high-stage cases (p=0.001) according to the Demicco classification. All relapses were associated with significant or high scores. (Table 7) Due to the low number of recurrences, multi-variable analysis could not be performed to compare the classifications.\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eMost SFTs present as benign behaviour.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e However, there have also been cases of benign to malignant transformation reported.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e Therefore, predicting tumors that may exhibit malignant behaviour is important in clinical practice. There are few studies in the literature on SFTs, including results from 50 or more patients who have undergone surgery, and these are generally multicentre. Consequently, more case series are needed to better analyse disease behaviour, follow-up, and treatment approaches. Our study aimed to identify factors affecting prognosis by analysing data on SFTs and to compare the performance of two grouping methods and three risk classification models proposed in the literature regarding prognosis and long-term follow-up results.\u003c/p\u003e\u003cp\u003eThe reported rate of malignancy in SFTs is 12\u0026ndash;37%.\u003csup\u003e1,5,18\u003c/sup\u003e Benign to malignant conversion has been reported in cases and is associated with size.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e Malignant tumors are expected to be larger, more symptomatic, atypically localised, younger in age, sessile, and multifocal.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan additionalcitationids=\"CR21 CR22 CR23\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e In our study, age was significantly higher in malignant patients (65\u0026thinsp;\u0026minus;\u0026thinsp;42) (p\u0026thinsp;=\u0026thinsp;0.001). Tumor size was numerically larger in malignant patients (11\u0026thinsp;\u0026minus;\u0026thinsp;8.5 cm) (p\u0026thinsp;=\u0026thinsp;0.150), and most of those with ki-67 (10% and above)\u0026thinsp;+\u0026thinsp;were in the malignant group (p\u0026thinsp;=\u0026thinsp;0.371).\u003c/p\u003e\u003cp\u003eRecurrences are observed more often in the first two to three years.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e Recurrence rates range from 0 to 17% in benign cases and from 13.6 to 66.7% in malignant ones cases.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e Sesile morphological type, resections larger than the wedge, and CD34 negativity are significant indicators of malignancy recurrence.\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e In our study cohort, 16.7% of recurrences occurred in patients with malignancies, with a median recurrence time of 36 months. Although no recurrence was observed in patients without mitosis, recurrences were seen in 3 patients with a mitosis count of 4 (10 HPF) or more and in 2 patients with a mitosis count of 4 (10 HPF) (p\u0026thinsp;=\u0026thinsp;0.023). Recurrences were only recorded in patients with necrosis (p\u0026thinsp;=\u0026thinsp;0.007), malignancy (p\u0026thinsp;=\u0026thinsp;0.046), and larger tumor size (p\u0026thinsp;=\u0026thinsp;0.022). Recurrence was more significant (p\u0026thinsp;=\u0026thinsp;0.012) in patients with ki-67 positivity\u0026thinsp;\u0026ge;\u0026thinsp;10%. Although the mean age of patients with recurrence was higher (65 vs. 57), the difference was not statistically significant (p\u0026thinsp;=\u0026thinsp;0.481). However, since malignancy is a major factor in recurrence and the mean age of malignant patients was higher (p\u0026thinsp;=\u0026thinsp;0.001), age has an indirect significance regarding recurrence. No correlation was found between pleomorphism and recurrence (p\u0026thinsp;=\u0026thinsp;0.230). Nonetheless, it was hypothesised that a significant correlation might exist because of the increase in cases, as these were observed exclusively in the malignant group.\u003c/p\u003e\u003cp\u003eMalignancy factors include originating from the parietal pleura or chest wall, isolated resection, malignant pleural effusion, large size (10 cm), mitotic number\u0026thinsp;\u0026gt;\u0026thinsp;10 (10 HPF), and a high proliferation rate. \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e The 5- and 10-year DFS rates are reported to be 82\u0026ndash;95% and 67-90.8%, respectively, and this rate is 58-72.1\u0026ndash;60.5% in the malignant group, and 95.7\u0026ndash;100% in the benign group (5 years only).\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e In our study, DFS was 96.4% at 2 years, 74.2% at 5 years, and 74.2% at 10 years. Since there was no recurrence in the benign group, it was 100%, while in the malignant group, it was 95% at 2 years, 61.8% at 5 years, and 61.8% at 10 years (p\u0026thinsp;=\u0026thinsp;0.107). Our findings show DFS rates align with the literature. There was a numerical difference between the benign and malignant groups, and we expect a statistically significant difference as the number of cases increases.\u003c/p\u003e\u003cp\u003eStudies have reported 5- and 10-year survival rates of 86\u0026ndash;94% and 72.1\u0026ndash;77%, respectively, with a median survival of 14\u0026ndash;24 years.\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e In benign SFT cases, 5-year survival rates are 89\u0026ndash;100%; in malignant cases, 5-year survival rates range from 45.5\u0026ndash;89%, and 10-year survival rates are 66.9%.\u003csup\u003e3,6,21\u0026ndash;23,26\u003c/sup\u003e We attribute the numerical differences between the results of the studies to variations in the number of malignant patients and surgeries. In our study, OS was 90% at 2 years, 67.7% at 5 years, and 51.6% at 10 years. OS in the benign group was 88.89% at all follow-up time points, whereas OS in the malignant group was 90.5% at 2 years, 59.9% at 5 years, and 37.4% at 10 years. The number of patients with malignancies was significantly higher in our patient population. Therefore, although our OS rate was slightly lower for all patients compared with that in the literature, the rate in patients with malignancies was comparable. The expected OS was 80.11 months in benign patients and 64.01 months in malignant cases (p\u0026thinsp;=\u0026thinsp;0.15). We believe that the statistical difference between the two groups will become more evident as the number of cases increases.\u003c/p\u003e\u003cp\u003eIn the study by Tan et al.\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, OS was 76% and DFS was 53% in malignant patients. When the survival graph from this study is analysed, it is observed that both rates are nearly equal during the first 2 years, with the disparity emerging after the 3rd year and then progressing in tandem with these rates. Similarly, in our study of malignant tumors, the difference widened after the 2nd year.\u003c/p\u003e\u003cp\u003eFactors affecting prognosis have been reported to include incomplete resection, recurrence, large size (10 cm), and pedicled genetic molecular factors encapsulated.\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e On the other hand, some authors have reported that tumor size, the pleura from which the tumor originates, or being symptomatic are not effective in prognosis.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e The most important prognostic factor related to surgical treatment is complete blockage removal resection.\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e In the study by Lahon et al.\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, which included multifactorial analysis, it was found that factors related to short-term survival in malignant tumors were vena cava compression, multifocality, resections larger than wedge, and recurrence, with recurrence being the most significant factor. In our study, the factors directly influencing prognosis were recurrence, malignancy, ki-67\u0026thinsp;\u0026gt;\u0026thinsp;10%, mitotic count of 4 (10 HPF) or more, necrosis; while the indirect factors were age, tumor size, and pleomorphism. Due to numerical limitations, we could not compare these factors through multifactorial analysis; however, the most impactful factor was recurrence based on individual assessments.\u003c/p\u003e\u003cp\u003eSurgery and chemoradiotherapy are employed in treating SFT. The timing of radiotherapy remains a contentious issue. Haas et al.\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e demonstrated that surgery combined with radiotherapy offers no significant advantage in overall survival (OS), although they recommend it for tumors with poor resection margins or high mitotic activity. Radiotherapy can influence surgical outcomes and potentially increase complication rates due to its effects on tissue. In our view, radiotherapy is a viable option following R1 resections, in cases of unresectable tumors, or with metastases.\u003c/p\u003e\u003cp\u003eSince anatomical classification systems cannot be used effectively, specialised classifications that are not based on large patient groups are employed to assess prognosis and recurrence.\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e The low incidence of SFT may be the reason. Apart from the definitions of malignancy, the authors developed their own scoring systems beyond malignancy criteria, incorporating factors that may influence prognosis and recurrence. They occasionally compared their scoring systems with others. New scoring studies are ongoing progress.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e While some authors have reported that isolated histological or morphological features can be useful for prediction, others have found that these alone are not enough. For example, in a study by Tan et al., recurrence rates were reported as 2%, 8%, 14%, and 63% according to Perrot's classification.\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e However, Tapias et al. found no significant difference in these parameters when comparing high- and low-risk groups according to Perrot and England's scoring.\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e In this study, the performance of these definitions, classifications, and systems was compared. All recurrences were observed in England's malignant group (p\u0026thinsp;=\u0026thinsp;0.046), de Perrot stage 3 (p\u0026thinsp;=\u0026thinsp;0.161), Tapias' cases with a total score of 3 and above (p\u0026thinsp;=\u0026thinsp;0.036), Diebold's cases with a total score of 2 and above (p\u0026thinsp;=\u0026thinsp;0.021), Demicco's stage 3 (p\u0026thinsp;=\u0026thinsp;0.001).\u003csup\u003e5,14,15,16,17\u003c/sup\u003e Based on these results, it was observed that England's criteria should be used for malignancy, de Perrot's classification was partially effective, and the Tapias, Diebold, and Demicco scoring systems were very successful in predicting recurrence. Given our current number of cases, we consider it premature to present a statistical comparison of the superiority of any one scoring system. We plan to include this analysis in future studies with a larger sample size. However, if we must comment, the modified Demicco classification was considered to be slightly superior to the other scoring systems because it assesses more variables, creates more groupings, and most of the recurrences in our study occurred in the highest scoring stage.\u003c/p\u003e\u003cp\u003e The weaknesses of our study included its retrospective, single-centre design and relatively small number of cases. We faced the challenge of studying a rare tumor, which prevented us from detecting a statistical difference in some instances where there was a numerical difference. Nevertheless, we gathered valuable data by comparing the effectiveness of all classifications used to predict SFT prognosis and behaviour.\u003c/p\u003e\u003cp\u003eAs a result, the factors directly affecting prognosis are malignancy, a mitotic count of 4 (10 HPF) or more, necrosis, recurrence, and ki-67\u0026thinsp;\u0026ge;\u0026thinsp;10%, while the factors indirectly influencing prognosis include increasing age, enlarging size, and pleomorphism. For malignancy criteria, England's standards should be applied, and de Perrot's classification is partly functional. The Tapias, Diebold, and Demicco scoring systems are highly effective in predicting recurrence and prognosis. However, the modified Demicco system is more useful and offers a higher level of evaluation. Studies with larger patient populations will help determine which scoring system is most effective, but this is likely to take a long time due to the rarity of the disease.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003e\u003cspan\u003eMindaye ET, Tesfaye GK, Aboye AG (2021) Intrathoracic giant solitary fibrous tumor of the pleura: Case report. Int J Surg Case Rep 85:106224. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.ijscr.2021.106224\u003c/span\u003e\u003c/span\u003eEpub 2021 Jul 22. PMID: 34311340; PMCID: PMC8326720\u003c/span\u003e\u003c/li\u003e\n \u003cli\u003e\u003cspan\u003eKhouzam MS, Khouzam N (2022) Malignant solitary fibrous tumor of the pleura. 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PMID: 32315454; PMCID: PMC7318349\u003c/span\u003e\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1 to 7 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Solitary Fibrous Tumor, England criteria, de Perrot classification, Tapias score, Diebold score, Demicco score","lastPublishedDoi":"10.21203/rs.3.rs-7552318/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7552318/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjectives\u003c/h2\u003e\u003cp\u003eBecause thoracic solitary fibrous tumors (SFTs) are rare, there is limited information on their clinical features, treatment, and follow-up. The literature mainly comprises individual case reports. Definitions, classifications, and scoring systems have been created to predict their clinical behaviour. Our study aimed to analyse SFT data to identify prognosis-related factors and to compare the performance of two describing approaches and three risk stratification models.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eMedical data from 37 patients, including 32 patients with SFT aged 18 years and older who underwent surgical treatment and five patients diagnosed by biopsy between 2004 and 2024, were analysed retrospectively. Parameters affecting recurrence and survival were investigated, and the effectiveness of existing classification and scoring systems was compared.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eFactors potentially associated with recurrence included four or more mitoses (10 HPF) (p\u0026thinsp;=\u0026thinsp;0.023), necrosis (p\u0026thinsp;=\u0026thinsp;0.007), at least 10% Ki-67 positivity (p\u0026thinsp;=\u0026thinsp;0.012), malignancy (p\u0026thinsp;=\u0026thinsp;0.046), and tumor size (p\u0026thinsp;=\u0026thinsp;0.022). Relapses were observed only in the malignant group according to the England classification (p\u0026thinsp;=\u0026thinsp;0.046), only in stage 3 according to the de Perrot classification (p\u0026thinsp;=\u0026thinsp;0.161), only in those with scores of three or higher according to the Tapias classification (p\u0026thinsp;=\u0026thinsp;0.036), only in those with scores of two or higher according to the Diebold classification (p\u0026thinsp;=\u0026thinsp;0.021), and all in high-stage groups (p\u0026thinsp;=\u0026thinsp;0.001) according to the Demicco classification. All recurrences occurred at significant or high scores.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e\u003cp\u003eThe factors directly affecting prognosis include malignancy, a mitotic count of 4 (10 HPF) or higher, necrosis, recurrence, and ki-67\u0026thinsp;\u0026ge;\u0026thinsp;10%, while indirectly influencing prognosis are increasing age, increasing size, and pleomorphism. For malignancy criteria, England's standards should be used, and de Perrot's classification is partly helpful. The Tapias, Diebold, and Demicco scoring systems are highly effective in predicting recurrence and prognosis. However, the modified Demicco system is more advantageous and offers a higher level of assessment.\u003c/p\u003e","manuscriptTitle":"Effectiveness of Classification and Scoring Systems in Solitary Fibrous Tumor Prognosis Prediction","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-09 13:44:37","doi":"10.21203/rs.3.rs-7552318/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"fc53b063-b6dc-483e-81d9-cc45a30b5876","owner":[],"postedDate":"September 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":54435133,"name":"Cardiothoracic Surgery"}],"tags":[],"updatedAt":"2025-09-09T13:44:37+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-09 13:44:37","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7552318","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7552318","identity":"rs-7552318","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}