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The clinical evolution of solitary fibrous tumors (SFTs) is often uncertain and several risk stratification systems (RSS) have been proposed. The Demicco et al. RSS is the most frequently implemented. In this study we aim to validate two alternative RSS (Sugita et al. and G-Score) using results for the Demicco RSS from a previous study of 97 SFTs. In addition, we aim to determine whether reclassified cases had any distinctive molecular features. As the Sugita et al. system substitutes mitotic count with Ki-67 index we also investigated whether Ki-67 results for tissue microarrays are comparable to those obtained using whole tissue sections. In the present study we detected that many cases classified by Demicco RSS as low-risk were reclassified as intermediate risk using the new system (G-score RSS). Kaplan-Meier survival plots for G-Score RSS showed that the low-risk and intermediate-risk SFTs had a similar evolution that contrasted with the more aggressive high-risk group. Moreover, the similar evolution in both low and intermediate-risk groups occurred despite the G-score system being stricter in classifying low-risk tumors. We observed that Sugita RSS does not provide any better risk stratification in comparison with the Demicco RSS, and testing both RSS in our series produced similar Kaplan-Meier survival data. We found some discordant results when comparing whole sections and the corresponding tissue microarrays samples, finding the hotspot areas easier to locate in whole sections. Forty-one SFTs with initial low-risk assigned by the Demicco RSS were reclassified as intermediate-risk by G-score finding both TP53 and HTER mutations in four cases, only HTER mutation in 11 cases, and only TP53 mutation in 2 cases. All six cases of SFT classified as high-risk by both the Demicco and G-score RSS suffered recurrence/metastasis, and half showed both TP53 and HTER mutations. Five SFTs were categorized as low-risk by both Demicco and G-score, of which 4 cases revealed HTER mutation. Regarding the outcome of these 5 patients, two were lost to follow-up, and one of the remaining three patients suffered recurrence. We believe that although the presence of both TP53 and HTER mutations may confer or be related to poor evolution, the isolated presence of HTER mutation alone would not necessarily be related to poor outcome. The G-score RSS more accurately identified low-risk patients than the other two risk models evaluated in the present series. Late recurrence/metastasis may occasionally be observed even in low-risk SFTs categorized by stricter classification systems such as the G-score RSS. These findings support the possibility that additional, as yet unknown factors may influence the clinical evolution of SFTs. In conclusion, given the possibility of late recurrence, long-term follow-up is recommended for all SFT patients, even in cases classified as low risk by the stricter G-score system. An integration of clinical, radiological, pathological, and molecular findings may improve SFT risk stratification and better predict patient outcome.

Although solitary fibrous tumors (SFTs) have an unpredictable evolution, some specific clinicopathologic factors have been associated with the final outcome. We retrieved clinical, pathological and molecular data of 97 patients with a histological diagnosis of SFT and Signal transducer and activator of transcription 6 (STAT6) positivity. We retrospectively studied the pathological factors predictive of recurrence/metastasis and compared them with the clinical outcome. A wide immunohistochemical study and molecular analysis to detect NAB2/STAT6 gene fusion, tumor protein-53 ( TP53) and/or (telomerase reverse transcriptase) TERT promotor mutation were performed. The risk of metastasis was calculated using the Demicco risk stratification system (RSS). The results were combined and examined to assess the accuracy of risk stratification and classification. The most common location was in non-extremities; 66% were located in soft tissue or subcutaneous areas and 92.8% in deep locations. On microscopic analysis, 38.1% of tumors revealed hypercellularity with a predominant patternless and/or hemangiopericytic growth pattern; 13.4% had ≥4 mitoses/10HPF; 16.5% showed necrosis, and almost half the tumors showed at least focal myxoid areas. Dedifferentiation was observed in three tumors. Immunomarker expression in SFTs was as follows: CD34 92.9%, CD99 57.1%, Bcl2 67.9%, neuroendocrine markers (at least 1) 25.7%, Desmin 14.3%, CK(AE1/AE3) 3%, Apoptotic Protease Activating Factor (APAF-1) 87% and finally Ki-67 ≥ 10% in 14.4%. The NAB2/STAT6 gene fusion was detected in 50 tumors. After a median follow-up of 90 months, 9.3% recurred, 11.3% metastasized, 10.3% died of disease and 76.2% were free of disease. TERT mutations were detected in 40.6% of the SFTs; the TP53 mutation was detected in 17%, and only 9.3% showed both mutations. According to the Demicco RSS, 6.1%, 11.3% and 82.4% of the tumors were classified as high, intermediate or low-risk of metastasis, respectively. All high-risk tumors had ≥4 mitoses/10HPF, necrosis, Ki-67 ≥ 10, HTER and/or TP53 mutation and poor evolution. The intermediate risk SFTs with worse evolution displayed the HTER mutation. Almost all low-risk tumors had a favorable evolution, although four showed at least one adverse factor (Ki-67 ≥ 10, ≥4 mitoses/10HPF or high tumor size) and had a worse evolution. An integration of clinical, morphologic, immunohistochemical and molecular findings may improve risk stratification and classification and better predict patient outcome. The unfavorable course seems to be more frequent in high-risk SFTs, although it is not exceptional in low-risk SFTs either; hence, a long-term follow-up is required independently of the assigned risk stratification score. The inclusion of molecular findings in risk stratification systems could improve the precision in the classification of SFTs, especially those of intermediate risk. Future studies will be required to determine the most effective way to incorporate molecular analyses into RSS on SFTs. The coexistence of several adverse factors such as ≥4 mitoses/10HPF, necrosis, Ki-67 ≥ 10%, mutations in HTER and/or p53 may suggest a closer clinical follow-up regardless of the histological appearance of the tumor.

Purpose: We aimed to explore the prognostic significance of collagen content in solitary fibrous tumors (SFTs) of the central nervous system (CNS) and preliminarily investigate its relationship with magnetic resonance imaging (MRI) features of SFTs. Methods: Collagen content was identified using Masson's trichrome staining, and quantitatively assessed. Radiomic methods were applied to extract quantitative MRI features of SFTs, which were then analyzed in relation to collagen content. Results: The collagen content in CNS SFTs was categorized into high- and low-content groups, with a cutoff value of 6%. Survival analysis indicated a positive correlation between collagen content and overall survival (OS). In multivariate Cox regression analysis, incorporating factors such as mitosis, necrosis, Ki67, and collagen content and other indicators, collagen content emerged as an independent prognostic factor. Collagen content demonstrated a negative correlation with tumor histological phenotype, Ki67, WHO grade, mitosis, necrosis, and brain invasion. Additionally, the signal intensity of SFTs on T2-weighted imaging (T2WI) decreased with increasing collagen content. Radiomics analysis identified 1,702 features from each patient's region of interest, with 12 features showing significant differences between the high and low collagen content groups. Among the quantitative parameters and radiomic models, the combined T1- and T2WI models exhibited the highest diagnostic performance. Conclusion: These findings suggest that collagen content is an independent prognostic risk factor for OS. Furthermore, combined radiomic models based on T1-and T2WI sequences may offer a more comprehensive, objective, and accurate assessment of collagen content in CNS SFTs. [ABSTRACT FROM AUTHOR]

We illustrated a rare case of malignant solitary fibrous tumor (MSFT) with epithelioid morphology in the occipital region of a 59-year-old female, in which a rare NAB2ex7-STAT6 exon15/16 double fusion subtype was detected by the Next-generation sequencing (NGS) and STAT6 immunohistochemistry (IHC) was diffusely and strongly positively expressed, without recurrence after 20 months of postoperative follow-up. The morphological and molecular genetic aspects and the differential diagnosis are described, and the relevant literature was assessed in order to broaden our understanding and diagnostic capability of this malignancy [ABSTRACT FROM AUTHOR]

Introduction: Solitary fibrous tumor (SFT) represents a fibroblastic neoplasm exhibiting NAB2::STAT6 gene rearrangement, displaying diverse clinical manifestations, spanning from benign to malignant. To predict prognosis, the modified (four-variable) Demicco (mDemicco) model was introduced. This investigation aims to authenticate the mDemicco risk model's precision in Asian patients while investigating the clinicopathological and molecular factors linked to the prognosis of extrameningeal SFTs. Methods: Clinicopathological data from 111 extrameningeal SFT cases in East China, covering the period from 2010 to 2020, were thoroughly analyzed. The tumors were classified using the mDemicco model . Immunohistochemical evaluation of P16 and P53, molecular detection of TP53 and TERT promoter mutation, and fluorescence in situ hybridization for CDKN2A gene alterations were performed. Statistical methods were utilized to assess the associations between clinicopathological or molecular factors and prognosis. Results: Histologically, only one parameter, the mitotic count, exhibited a statistical correlation with progression-free survival (PFS) and overall survival (OS). During the Kaplan-Meier analysis, the variation in PFS among the different risk groups exhibited a notable trend towards statistical significance. Nevertheless, 3 out of 74 patients classified as low-risk SFTs and 7 out of 21 patients classified as intermediate-risk exhibited disease progression. Among the 5 patients with TP53 mutations and/or mutant-type P53 immunophenotype, 3 experienced disease progression, including 2 intermediate-risk patients. Additionally, among the 4 patients with TERT promoter mutations who were followed up, 3 showed progression, including 2 intermediate-risk patients. Moreover, it was observed that hemizygous loss of CDKN2A was detected in more than 30% of one case, yet the patient exhibited a favorable survival outcome. Conclusion: The mDemicco risk model exhibits certain limitations when dealing with smaller tumor sizes, younger age groups, and occurrences of malignant and dedifferentiated SFTs. Furthermore, molecular factors, such as TP53 or TERT promoter mutations, may identify intermediate-risk SFTs with poorer prognoses. [ABSTRACT FROM AUTHOR]

Background: Accurate preoperative histological stratification (HS) of intracranial solitary fibrous tumors (ISFTs) can help predict patient outcomes and develop personalized treatment plans. However, the role of a comprehensive model based on clinical, radiomics and deep learning (CRDL) features in preoperative HS of ISFT remains unclear., Purpose: To investigate the feasibility of a CRDL model based on magnetic resonance imaging (MRI) in preoperative HS in ISFT., Study Type: Retrospective., Population: Three hundred and ninety-eight patients from Beijing Tiantan Hospital, Capital Medical University (primary training cohort) and 49 patients from Lanzhou University Second Hospital (external validation cohort) with ISFT based on histopathological findings (237 World Health Organization [WHO] tumor grade 1 or 2, and 210 WHO tumor grade 3)., Field Strength/sequence: 3.0 T/T1-weighted imaging (T1) by using spin echo sequence, T2-weighted imaging (T2) by using fast spin echo sequence, and T1-weighted contrast-enhanced imaging (T1C) by using two-dimensional fast spin echo sequence., Assessment: Area under the receiver operating characteristic curve (AUC) was used to assess the performance of the CRDL model and a clinical model (CM) in preoperative HS in the external validation cohort. The decision curve analysis (DCA) was used to evaluate the clinical net benefit provided by the CRDL model., Statistical Tests: Cohen's kappa, intra-/inter-class correlation coefficients (ICCs), Chi-square test, Fisher's exact test, Student's t-test, AUC, DCA, calibration curves, DeLong test. A P value <0.05 was considered statistically significant., Results: The CRDL model had significantly better discrimination ability than the CM (AUC [95% confidence interval, CI]: 0.895 [0.807-0.912] vs. 0.810 [0.745-0.874], respectively) in the external validation cohort. The CRDL model can provide a clinical net benefit for preoperative HS at a threshold probability >20%., Data Conclusion: The proposed CRDL model holds promise for preoperative HS in ISFT, which is important for predicting patient outcomes and developing personalized treatment plans., Level of Evidence: 3 TECHNICAL EFFICACY: Stage 2., (© 2023 International Society for Magnetic Resonance in Medicine.)

Solitary fibrous tumor (SFT) is a relatively rare type of mesenchymal neoplasm that occurs most frequently in the pleura. However, SFT originating from the prostate is particularly uncommon and only approximately 39 cases were reported before. Herein, we reported a rare case of a patient diagnosed with prostate SFT and presented a literature review. Case presentation: A 50-year-old Asian with irritative urinary symptoms was admitted to our hospital and almost all the evidence indicated that benign prostate hyperplasia (BPH) caused his symptoms. Therefore, transurethral resection of the prostate (TURP) was performed, but histopathological and Immunohistochemical (IHC) assessments showed that spindle cells arranged disorderly in the TURP specimen with a cluster of differentiation 34 (CD34), B-cell lymphoma-2 (Bcl-2), and signal transducer and activator of transcription 6 (STAT6) highly expressed and SFT was diagnosed. Finally, the patient underwent a radical prostatectomy and there was no disease progression observed thereafter. Prostate SFT is extremely rare, and to our knowledge, this is the first case of prostate SFT that is difficult to differentiate from small volume BPH. IHC examinations are of great diagnostic value. Radical resection of the tumor appears to be the most effective method at present and continuous follow-up is highly recommended. [ABSTRACT FROM AUTHOR]

Background: To date, published studies have shown that 18F-FDG PET/CT and CT have limited value in differentiating benign and malignant solitary fibrous tumours of the pleura (SFTP). This study aimed to determine whether the metabolic and morphological characteristics of 18F-FDG PET/CT can be a valuable addition to diagnostic tools for SFTPs.Methods: From January 2016 to November 2021, we performed a retrospective review in 32 SFTPs patients who underwent 18F-FDG PET/CT scan. All the SFTP diagnoses were confirmed by surgical resection or biopsy samples. The metabolic parameters (including SUVmax, SUVmean, MTV, TLG, and SULmax) were obtained from 18F-FDG PET/CT images.Results: Thirty-two patients with SFTP were consecutively identified. The malignant SFTPs have higher Ki-67 expression (P = 0.005). The study observed that tumour heterogeneity without contrast injection (P = 0.001) and intratumor blood vessels (P = 0.047) were morphological features associated with malignant SFTP. Malignant SFTP was more frequently observed with higher SUVmax values (P = 0.001), higher SUVmean values (P = 0.001), higher TLG values (P = 0.006), and higher SULmax values (P < 0.001). For predicting malignant SFTP, the AUC values of SUVmax, SUVmean, TLG, and SULmax obtained by the area under curve analysis were 0.970 (95% CI 0.907-1.000; P = 0.001), 0.874 (95% CI 0.675-1.000; P = 0.009), 0.807 (95% CI 0.654-0.961; P = 0.031), and 0.911 (95% CI 0.747-1.000; P = 0.004), respectively.Conclusion: The study showed that metabolic and morphological features were useful for distinguishing malignant from benign SFTPs. [ABSTRACT FROM AUTHOR]

Background: To date, published studies have shown that 18 F-FDG PET/CT and CT have limited value in differentiating benign and malignant solitary fibrous tumours of the pleura (SFTP). This study aimed to determine whether the metabolic and morphological characteristics of 18 F-FDG PET/CT can be a valuable addition to diagnostic tools for SFTPs., Methods: From January 2016 to November 2021, we performed a retrospective review in 32 SFTPs patients who underwent 18 F-FDG PET/CT scan. All the SFTP diagnoses were confirmed by surgical resection or biopsy samples. The metabolic parameters (including SUVmax, SUVmean, MTV, TLG, and SULmax) were obtained from 18 F-FDG PET/CT images., Results: Thirty-two patients with SFTP were consecutively identified. The malignant SFTPs have higher Ki-67 expression (P = 0.005). The study observed that tumour heterogeneity without contrast injection (P = 0.001) and intratumor blood vessels (P = 0.047) were morphological features associated with malignant SFTP. Malignant SFTP was more frequently observed with higher SUVmax values (P = 0.001), higher SUVmean values (P = 0.001), higher TLG values (P = 0.006), and higher SULmax values (P < 0.001). For predicting malignant SFTP, the AUC values of SUVmax, SUVmean, TLG, and SULmax obtained by the area under curve analysis were 0.970 (95% CI 0.907-1.000; P = 0.001), 0.874 (95% CI 0.675-1.000; P = 0.009), 0.807 (95% CI 0.654-0.961; P = 0.031), and 0.911 (95% CI 0.747-1.000; P = 0.004), respectively., Conclusion: The study showed that metabolic and morphological features were useful for distinguishing malignant from benign SFTPs., (© 2022. The Author(s) under exclusive licence to The Japanese Society of Nuclear Medicine.)

Malignant solitary fibrous tumor (SFT) in the retroperitoneum is rare. The present study reported on the case of a 67-year-old man who had retroperitoneal SFT for ~13 years, which resulted in two recurrences and lymphatic metastases. After the second recurrence, the patient presented with hematochezia and multiple retroperitoneal masses were found through computed tomography (CT). Histopathological examination showed that the tumor was mainly comprised of short spindle cells, arranged into sparse and dense areas. Mitotic figures were observed, generally 6–8 mitoses/10 high power fields, along with local necrosis. The tumor invaded the circumferential liver, intestines, lymphatic vessels and lymph nodes. Combined with the immunohistochemical results, it was diagnosed as a malignant SFT, which regrew just 2 months after the latest surgery. Retroperitoneal SFTs with repeated relapses, infiltrative growth and lymphatic metastasis suggest the need for careful and long-term follow-up. [ABSTRACT FROM AUTHOR]