Evaluation of NAB2-STAT6 Fusion Variants and Other Molecular Alterations as Prognostic Biomarkers in a Case Series of 83 Solitary Fibrous Tumors

Immunotherapy for Solitary Fibrous Tumor (Hemangiopericytoma): A Unique Treatment Approach for a Rare Central Nervous System Tumor

INTRODUCTION

Solitary fibrous tumors (SFTs) of the central nervous system represent a unique entity with limited data on best treatment practices.

CASE REPORT

Here, we present a case of multiply recurrent central nervous system SFT treated with radiation and immunotherapy. Immunotherapy was chosen based on mutations of genes encoding DNA repair enzymes detected through next-generation sequencing of the tumor, DNA polymerase epsilon catalytic subunit ( POLE ) and mutL homolog 1. The use of radiation and immunotherapy led to slight shrinkage and no recurrence of the tumor for over 2 years.

CONCLUSION

The presence of somatic DNA repair enzyme gene mutations in SFT may suggest a benefit from a combination of radiotherapy and immunotherapy. This may serve as a biomarker for guiding management in patients with this rare tumor.

Establishing biomarkers for soft tissue sarcomas

INTRODUCTION

Soft tissue sarcomas (STS) are a rare and diverse group of tumors. Curative options are limited to localized disease, with surgery being the mainstay. Advanced stages are associated with a poor prognosis. Currently, the prognosis of the patient is based on histological classification and clinical characteristics, with only a few biomarkers having entered clinical practice.

AREAS COVERED

This article covers extensive recent research that has established novel potential biomarkers based on genomics, proteomics, and clinical characteristics. Validating and incorporating these biomarkers into clinical practice can improve prognosis, prediction of recurrence, and treatment response. Relevant literature was collected from PubMed, Scopus, and clinicaltrials.gov databases (November 2023).

EXPERT OPINION

Currently, defining prognostic markers in soft tissue sarcomas remains challenging. More studies are required, especially to personalize treatment through advanced genetic profiling and analysis using individual tumor and patient characteristics.

Exploring Solitary Fibrous Tumors at a Tertiary Cancer Center: Clinicopathological and Immunomorphologic Profile

Background Solitary fibrous tumor (SFT) is a distinct fibroblastic tumor that can occur at any anatomical site and can manifest a variety of histopathological features. NAB2-STAT6 gene fusion has recently emerged as a sensitive and specific molecular marker and its surrogate on immunohistochemistry, STAT6 has also displayed considerable efficacy. Nevertheless, its histologic diversity can result in diagnostic challenges, especially when classic features are not apparent. Methods A retrospective study was conducted at a tertiary cancer centre in North India over 3 years to document the clinicopathologic and immunomorphologic profile of SFTs. Immunohistochemical analysis of BCOR and p53 were gauged additionally and patients were stratified according to Modified Demicco and Salas criteria for risk of metastasis. Results Sixteen patients of SFT were identified, affecting middle-aged men and women equally. Though lung/pleura are known to be involved commonly, SFT affects other sites such as the kidney, brain, buccal mucosa, liver, and penis as well. The majority endured localized disease while a lesser number suffered locoregional/distant spread. Two patients revealed features of a malignant profile. Risk stratification according to the Modified Demicco and Salas criteria evinced comparable results. No discernible relationship however was highlighted between the immunohistochemical expression of BCOR, p53, and any significant SFT parameter. Conclusion Although SFTs are very rare substantially benign mesenchymal neoplasms, pathologists must be conversant with their histological diversity and be vigilant of their malignant attributes. The worth of STAT6 immunohistochemistry for precise diagnosis and long-term studies for delineating clinical behavior cannot be overemphasized.

Risk factors for recurrent disease after resection of solitary fibrous tumor: a systematic review

Introduction

Solitary fibrous tumor (SFT) is a rare soft tissue tumor found at any site of the body. The treatment of choice is surgical resection, though 10%-30% of patients experience recurrent disease. Multiple risk factors and risk stratification systems have been investigated to predict which patients are at risk of recurrence. The main goal of this systematic review is to create an up-to-date systematic overview of risk factors and risk stratification systems predicting recurrence for patients with surgically resected SFT within torso and extremities.

Method

We prepared the review following the updated Prisma guidelines for systematic reviews (PRISMA-P). Pubmed, Embase, Cochrane Library, WHO international trial registry platform and ClinicalTrials.gov were systematically searched up to December 2022. All English studies describing risk factors for recurrence after resected SFT were included. We excluded SFT in the central nervous system and the oto-rhino-laryngology region.

Results

Eighty-one retrospective studies were identified. Different risk factors including age, symptoms, sex, resection margins, anatomic location, mitotic index, pleomorphism, hypercellularity, necrosis, size, dedifferentiation, CD-34 expression, Ki67 index and TP53-expression, APAF1-inactivation, TERT promoter mutation and NAB2::STAT6 fusion variants were investigated in a narrative manner. We found that high mitotic index, Ki67 index and presence of necrosis increased the risk of recurrence after surgically resected SFT, whereas other factors had more varying prognostic value. We also summarized the currently available different risk stratification systems, and found eight different systems with a varying degree of ability to stratify patients into low, intermediate or high recurrence risk.

Conclusion

Mitotic index, necrosis and Ki67 index are the most solid risk factors for recurrence. TERT promoter mutation seems a promising component in future risk stratification models. The Demicco risk stratification system is the most validated and widely used, however the G-score model may appear to be superior due to longer follow-up time.

Systematic Review Registration

CRD42023421358.

Long-Term Surgical Outcome for Orbital Solitary Fibrous Tumors

PURPOSE

To report long-term outcomes after surgery for orbital solitary fibrous tumors.

METHODS

Retrospective review of patients with orbital solitary fibrous tumor, first seen between 1971 and 2022. Primary excisions were grouped as (A) surgically intact, (B) macroscopic, but with cell spillage, or (C) known incomplete excision.

RESULTS

Fifty-nine patients (31 female; 53%) presented at a mean age of 43.0 years (19-82 years), with 5 patients (8.5%) having malignant solitary fibrous tumors. Average follow up was 11.4 years (median 7.8; range 1-43 years). There were 28 of 59 (47%) group A patients with 1 of 28 (3%) having recurrence, 20 of 59 (34%) group B having 6 of 20 (30%) recurrences, and 11 of 59 (19%) group C with 9 of 11 (82%) recurrence ( p < 0.001 for recurrence rate). At a mean of 8.9 (range 1-23.6) years after initial treatment, continued local tumor growth was evident in 16 (27%) patients, with higher-grade recurrence in 3 of 14 (21%) cases. No patient had systemic disease at presentation, but 2 of 59 patients (3%) developed metastases at 22 and 30 years after first treatment. The 10-year progression-free survival was 94% (group A), 60% (group B), and 36% (group C). Tumor disruption or incomplete excision (groups B + C) carries the highest risk of tumor recurrence (hazard ratio 15.0; 95% confidence interval, 1.98-114; p = 0.009), with no correlation to tumor size or histology.

CONCLUSIONS

Orbital solitary fibrous tumors have a low recurrence rate with surgically intact excision; piecemeal excision, capsular disruption, or known incomplete resection have a high recurrence rate, which can occur decades later. Baseline postoperative scans is recommended, together with long-term clinical and interval imaging.

Extra-meningeal solitary fibrous tumor: an evolving entity with chameleonic morphological diversity, a hallmark molecular alteration and unresolved issues in risk stratification assessment

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

A review of solitary fibrous tumours of the orbit and ocular adnexa

Solitary fibrous tumour (SFT) is an uncommon spindle cell tumour of mesenchymal origin characterised by NAB2-STAT6 gene fusion. Although it was first described in the pleura, it can occur in connective tissue in any part of the body, but rarely presents in the orbit and ocular adnexa. SFT, which is part of the same disease spectrum as other fibroblastic tumours such as giant cell angiofibroma, haemangiopericytoma and fibrous histiocytoma, usually presents as a painless, slow-growing mass in any age group and generally follows a benign course, with a good prognosis after complete excision. However, malignant forms rarely occur. Even for benign tumours a more aggressive clinical behaviour is possible, with relentless infiltrative local growth, frequent recurrence following surgery, and malignant transformation with the potential for metastatic spread. Careful long-term follow-up is essential. The published literature on SFTs of the orbit and ocular adnexa is reviewed, and the aetiology, clinical presentation, epidemiology, radiological features, histopathology, immunohistochemistry, risk stratification, clinical management, and prognosis are discussed, reflecting on our own experience.

A Single-Center Retrospective Analysis of Intracranial and Spinal Solitary Fibrous Tumor/Hemangiopericytoma Clinical Outcomes: Sex Association With Aggressiveness

BACKGROUND

Solitary fibrous tumor/hemangiopericytoma (SFT/HPCT) is a rare tumor characterized by high recurrence rate and metastatic potential, even after surgical resection. We report on the clinical outcomes and risk factors for metastasis and progression-free survival (PFS) of patients diagnosed with SFT/HPCT.

METHODS

We retrospectively identified patients with intracranial or spinal SFT/HPCT who underwent surgical resection and/or radiation therapy at our institution between 1995 and 2021. Baseline demographics, tumor characteristics, and outcome data were collected, and factors associated with PFS and metastasis were analyzed.

RESULTS

Thirty-four subjects (mean age, 46.4 years; 44% female) with a histopathologically proven diagnosis of SFT/HPCT were included; the median follow-up was 89.7 months. Twenty-two tumors were supratentorial (67%), 6 (18%) were infratentorial, and 5 (15%) were spinal. Eleven patients had documented occurrence of metastasis (32%). Detailed preoperative and postoperative data were available for 25 patients (74%) who received treatment at our institution after their initial diagnosis. Of those, 20 (80%) underwent gross total resection (GTR), and 12 (48%) received either adjuvant or salvage radiotherapy. Univariate analyses revealed that males had a shorter mean PFS compared with females (25 months vs. 78 months; P = 0.01), and that patients who underwent GTR had a longer mean PFS compared with those who underwent subtotal resection (54 months vs. 23 months; P = 0.02). Male sex was the sole risk factor for metastasis (odds ratio, 6.75; 95% confidence interval, 1.19-38.02).

CONCLUSIONS

Our data demonstrate a strong association between male sex and the outcomes of shorter PFS and higher risk for metastases. Further research is warranted to understand the clinical characteristics and outcomes of this rare tumor.

Molecular testing of soft tissue tumors

BACKGROUND

The diagnosis of soft tissue tumors is challenging, especially when the evaluable material procured is limited. As a result, diagnostic ancillary testing is frequently needed. Moreover, there is a trend in soft tissue pathology toward increasing use of molecular results for tumor classification and prognostication. Hence, diagnosing newer tumor entities such as CIC-rearranged sarcoma explicitly requires molecular testing. Molecular testing can be accomplished by in situ hybridization, polymerase chain reaction, as well as next generation sequencing, and more recently such testing can even be accomplished leveraging an immunohistochemical proxy.

CONCLUSION

This review evaluates the role of different molecular tests in characterizing soft tissue tumors belonging to various cytomorphologic categories that have been sampled by small biopsy and cytologic techniques.

Evaluation of Alternative Risk Stratification Systems in a Large Series of Solitary Fibrous Tumors with Molecular Findings and Ki-67 Index Data: Do They Improve Risk Assessment?

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.

Tumor Fibroso Solitário Primário em Região Pélvica: Relato de Caso

Introdução: O tumor fibroso solitário é uma neoplasia mesenquimal rara, originada de células intersticiais dendríticas CD34 positivas e composta pela justaposição de células fusiformes. Os casos iniciais foram primariamente descritos na região torácica, e o principal sítio, a pleura visceral. Raramente são descritos casos de tumor fibroso solitário extrapleural em região pélvica, demonstrando a possibilidade de múltiplas sítios primários. Relato do caso: Paciente de 38 anos, sexo feminino, previamente saudável e assintomática, procurou orientação médica após uma ultrassonografia pélvica de rotina evidenciar uma imagem heterogênea na região anexial direita, paraovariana, sendo submetida à ressecção cirúrgica da lesão, com diagnóstico de tumor fibroso solitário confirmado por imuno-histoquímica. Discutem-se os aspectos do diagnóstico imuno-histoquímico e do tratamento cirúrgico. Conclusão: Os casos de tumor fibroso solitário em região pélvica podem ser descobertos por meio de ultrassonografia pélvica de rotina. O tratamento cirúrgico, com ressecção ampliada e margens negativas, deve ser o principal objetivo nos casos de tumor fibroso solitário em região pélvica. A obtenção de amostras para análise imuno-histoquímica é recomendada, e a positividade para CD34 e STAT6 aponta o diagnóstico. Recidivas podem ocorrer em até uma década de seguimento, sendo recomendado período longo de acompanhamento pós-cirúrgico.

Solitary fibrous tumor of the liver: A case report and review of the literature

BACKGROUND

Hepatic solitary fibrous tumor (SFT) is a rare neoplasm. Up to now, only 90 cases have been reported in the English language literature. This report describes a case of SFT of the liver misdiagnosed as hepatocellular carcinoma.

CASE SUMMARY

A 42-year-old male had a two-year history of a gradually enlarging intrahepatic nodule. The preoperative imaging revealed a mass with a size of 2.7 cm × 2.3 cm located in the segment IV of the liver. The patient was subjected to the resection of the segment IV, such as the medial segment of the left lobe of the liver. The histological examination of the mass showed various spindled cells irregularly arranged in the stroma. The immunohistochemistry of this mass revealed a positive staining for CD34 and STAT6. The history of intracranial tumor and postoperative pathological results led to the diagnosis of SFT of the liver (SFTL) due to a metastasis from the brain.

CONCLUSION

SFTL is an uncommon mesenchymal neoplasm that can be easily overlooked or misdiagnosed. The best treatment choice is the complete surgical resection of the mass. A regular follow-up after the surgery should be performed due to the poor prognosis of metastatic or recurrent SFT.