Round cell sarcomas – Biologically important refinements in subclassification

Clinical Characteristics of Children with Nasal BCOR-Rearranged Ewing-like Sarcoma: A Case Report and Literature Review

Ewing-like sarcomas (ELS) are round cell mesenchymal neoplasms that are highly aggressive to bone and/or soft tissue. However, they rarely occur in the nose, with no reported such cases in the medical literature to date. Here, we reported the case of a two-year-old Chinese boy who presented with a mass in the left nasal cavity. Surprisingly, the final histopathological diagnosis of the nasal mass was determined to be a subtype of ELS, BCOR-rearranged sarcoma. Therefore, we retrospectively analyzed the clinical data of this case and reviewed the relevant literature on ELS and BCOR-rearranged sarcoma. The purpose of this article is to provide new insights into the clinical characteristics of children with BCOR-rearranged Ewing-like sarcoma and to improve the understanding of this disease.

A rare Ewing-like small round cell tumor in prostate: a case report and literature review

BACKGROUND

Small round cell tumor (SRCT) is a group of malignancy with similar optical microscopic morphology. Despite its low incidence, SRCT has a high malignant degree and poor prognosis. Besides, atypical clinical symptoms make it difficult in preoperative diagnosis.

CASE REPORT

A 67-year-old man was presented to the outpatient service with dysuria and weak urine stream lasting for 3 months. After oral treatment with tamsulosin and finasteride for 2 months, the symptoms worsen. Transurethral prostate holmium laser enucleation was operated and postoperative pathology result revealed small blue round cell malignant tumor. Further immunohistochemistry and fluorescence in situ hybridization examination indicated Ewing-like SRCT. So a Da Vinci Robotic prostatectomy was performed further and whole-genome sequencing was conducted. Several gene mutations including RAF1, ARID1A, SMARCA4, and BCL2L11 were found but no FDA-approved drug could treat specifically. Then the patient received Ewing-type therapeutic regimens treatment and has been followed up to date (over 24 months).

CONCLUSION

Because of its non-elevated serum PSA level, prostate SRCT is often ignored as a possibility of malignant tumor and regarded as benign prostatic hyperplasia (BPH). The possibility of prostate SRCT need to be considered if dysuria symptoms could not alleviate significantly after a period of oral treatment.

Gene partners of the EWSR1 fusion may represent molecularly distinct entities

EWSR1 fusions are highly promiscuous and are associated with unique malignancies, clinical phenotypes, and molecular subtypes. However, rare fusion partners (RFP) of EWSR1 has not been well described. Here, we conducted a cross-sectional, retrospective study of 1,140 unique tumors harboring EWSR1 fusions. We identified 64 unique fusion partners. RFPs were identified more often in adults than children. Alterations in cell cycle control and DNA damage response genes as driving the differences between fusion partners. Potentially clinically actionable genomic variants were more prevalent in tumors harboring RFP than common fusions. While the data presented here is limited, tumors harboring RFP of EWSR1 may represent molecularly distinct entities and may benefit from further molecular testing to identify targeted therapeutic options.

Chemotherapeutic drugs for soft tissue sarcomas: a review

Despite the low incidence of soft tissue sarcomas (STSs), hundreds of thousands of new STS cases are diagnosed annually worldwide, and approximately half of them eventually progress to advanced stages. Currently, chemotherapy is the first-line treatment for advanced STSs. There are difficulties in selecting appropriate drugs for multiline chemotherapy, or for combination treatment of different STS histological subtypes. In this study, we first comprehensively reviewed the efficacy of various chemotherapeutic drugs in the treatment of STSs, and then described the current status of sensitive drugs for different STS subtypes. anthracyclines are the most important systemic treatment for advanced STSs. Ifosfamide, trabectedin, gemcitabine, taxanes, dacarbazine, and eribulin exhibit certain activities in STSs. Vinca alkaloid agents (vindesine, vinblastine, vinorelbine, vincristine) have important therapeutic effects in specific STS subtypes, such as rhabdomyosarcoma and Ewing sarcoma family tumors, whereas their activity in other subtypes is weak. Other chemotherapeutic drugs (methotrexate, cisplatin, etoposide, pemetrexed) have weak efficacy in STSs and are rarely used. It is necessary to select specific second- or above-line chemotherapeutic drugs depending on the histological subtype. This review aims to provide a reference for the selection of chemotherapeutic drugs for multi-line therapy for patients with advanced STSs who have an increasingly long survival.

Molecular classification of soft tissue sarcomas for adequate diagnosis: A study on the northeast population of Morocco

Background

Soft tissue sarcomas (STS) are a heterogeneous group of tumors. For adequate therapeutic management, an accurate diagnosis is necessary. In Morocco, the diagnosis is essentially based on the morphological and immunohistochemical study. Compared to other techniques, fluorescence in situ hybridization (FISH) is easier to develop and less expensive. This study aims to assess the feasibility and utility of implementing FISH technique to improve diagnostic accuracy and establish a good classification.

Material and methods

This is a retrospective cohort study. 211 cases of mesenchymal tumors were included. Hematoxylin Eosin Safran (HES) staining was performed in all cases followed by immunohistochemistry (IHC). FISH was performed in all cases with suspected STS. The probes used were EWSR1, MDM2 and SS18. The performance of FISH and histopathological test were evaluated by the ROC curve method (receiver operating characteristic). We evaluated the concordance between FISH and real time PCR by Cohen test.

Results

The real-time PCR technique showed good agreement with the FISH test by a Kappa coefficient of 60% (p = 0.035). FISH was able to confirm that it is more accurate (Youden's Index = 91%) than histological/immunohistochemical analysis (Youden's Index = 51%), as well as the positive predictive value was higher (100%) with an ROC curve finding a larger area under the curve of 0.953 (95% CI: 0.918-0.988), p = 0.000 which supports that FISH shows high performance to present an accurate final diagnosis.

Conclusion

This is the first and the largest Moroccan series for the molecular diagnosis of STS by FISH. Our study shows that paraffin FISH is a sensitive and specific ancillary tool in the diagnosis of STS when used in the appropriate clinicopathological context.

WEE1 kinase is a therapeutic vulnerability in CIC-DUX4 undifferentiated sarcoma

CIC-DUX4 rearrangements define an aggressive and chemotherapy-insensitive subset of undifferentiated sarcomas. The CIC-DUX4 fusion drives oncogenesis through direct transcriptional upregulation of cell cycle and DNA replication genes. Notably, CIC-DUX4–mediated CCNE1 upregulation compromises the G₁/S transition to confer a dependence on the G₂/M cell cycle checkpoint. Through an integrative transcriptional and kinase activity screen using patient-derived specimens, we now show that CIC-DUX4 sarcomas depend on the G₂/M checkpoint regulator WEE1 as part of an adaptive survival mechanism. Specifically, CIC-DUX4 sarcomas depended on WEE1 activity to limit DNA damage and unscheduled mitotic entry. Consequently, genetic or pharmacologic WEE1 inhibition in vitro and in vivo led to rapid DNA damage–associated apoptotic induction of patient-derived CIC-DUX4 sarcomas. Thus, we identified WEE1 as a vulnerability targetable by therapeutic intervention in CIC-DUX4 sarcomas.

Non-rhabdomyosarcoma soft tissue sarcomas diagnosed in patients at a young age. An overview of clinical, pathological, and molecular findings

OBJECTIVE

Disease spectrum in pediatric sarcoma differs substantially from adults. We report a cohort of very young children with non-rhabdomyosarcoma soft tissue sarcoma (NRSTS) detailing their molecular features, treatment, and outcome.

METHODS

We report features of consecutive children (age <2 years) with NRSTS (2000-2017). Archival pathological material was re-reviewed, with additional molecular techniques applied where indicated.

RESULTS

Twenty-nine patients (16 females, 55%) were identified (median age 6 months; range 0-23). Most common diagnoses included infantile fibrosarcoma (IFS, n = 14, 48%), malignant rhabdoid tumor (MRT, n = 4, 14%), and undifferentiated sarcoma (n = 4, 14%). Twenty-seven of 29 (93%) had tumor molecular characterization to confirm diagnosis. Clinical presentation included a swelling/mass (n = 23, 79%). Disease extent was localized (n = 20, 69%), locoregional (n = 6, 21%), or metastatic (n = 3, 10%). Seventeen of 29 (59%) who underwent surgery achieved complete resection (R0). Other treatments included conventional chemotherapy (n = 26, 90%), molecularly targeted therapies (n = 3, 10%), and radiation (n = 5, 17%). At last follow-up (median 3 years; range 0.3-16.4), 23 (79%) were alive, disease-free and six (21%) had died of disease. All patients with IFS were alive and all those with MRT died. A cancer predisposition syndrome (CPS) was confirmed in three of 10 (30%) genetically tested patients.

CONCLUSION

We recommend tumor molecular characterization in all young patients including evaluation for CPS to optimize treatment options and prognostication.

A Case Series of BCOR Sarcomas With a New Splice Variant of BCOR/CCNB3 Fusion Gene

BACKGROUND/AIM

Undifferentiated round cell sarcomas are a heterogeneous group of sarcomas. Identification of BCOR alterations, such as BCOR/CCNB3 and BCOR/MAML3 fusion genes and BCOR ITD has recently contributed in the precise diagnosis of these neoplasms, defining a new entity of the current classification of soft tissue and bone sarcomas. BCOR sarcomas share both morphological and genetic characteristics distinct from Ewing sarcomas. The scope of our study was to retrospectively identify BCOR sarcomas and find the correlations with the clinical outcome of these patients.

PATIENTS AND METHODS

Histopathology and immunohistochemistry of pediatric tumor samples were combined with molecular testing (PCR) and fluorescent in situ hybridization to find BCOR sarcomas.

RESULTS

We, herein, present our experience with BCOR sarcomas in a referral center of Greece. Moreover, we report in one case the detection of a variant BCOR/CCNB3 fusion not previously described.

CONCLUSION

We are the first to report a splice variant of BCOR/CCNB3 which reveals the central position of BCOR in the oncogenesis of these tumors, furthermore we highlight the importance of molecular diagnostics in Ewing-like sarcomas and discuss the current treatment options for this rare entity.

Integrated diagnosis based on transcriptome analysis in suspected pediatric sarcomas

Pediatric solid tumors are a heterogeneous group of neoplasms with over 100 subtypes. Clinical and histopathological diagnosis remains challenging due to the overlapping morphological and immunohistochemical findings and the presence of atypical cases. To evaluate the potential utility of including RNA-sequencing (RNA-seq) in the diagnostic process, we performed RNA-seq in 47 patients with suspected pediatric sarcomas. Histopathologists specialized in pediatric cancer re-evaluated pathological specimens to reach a consensus diagnosis; 42 patients were diagnosed with known subtypes of solid tumors whereas 5 patients were diagnosed with undifferentiated sarcoma. RNA-seq analysis confirmed and refined consensus diagnoses and further identified diagnostic genetic variants in four of the five patients with undifferentiated sarcoma. Genetic lesions were detected in 23 patients, including the novel SMARCA4-THOP1 fusion gene and 22 conventional or recently reported genetic events. Unsupervised clustering analysis of the RNA-seq data identified a distinct cluster defined by the overexpression of rhabdomyosarcoma-associated genes including MYOG and CHRNG. These findings suggest that RNA-seq-based genetic analysis may aid in the diagnosis of suspected pediatric sarcomas, which would be useful for the development of stratified treatment strategies.

Meta-analysis of BCOR rearranged sarcomas: challenging the therapeutic approach

INTRODUCTION

BCOR rearranged sarcomas comprise a group of malignant mesenchymal tumors that until recently were classified as Ewing sarcomas or as undifferentiated round cell sarcomas. The identification of alterations involving BCOR gene such as BCOR-CCNB3, BCOR-MAML3, ZC3H7B-BCOR fusion genes and BCOR internal tandem duplication (ITD) is characteristic for the differential diagnosis of BCOR rearranged sarcomas. Due to the rarity of these tumors there is no consensus or guidelines regarding the optimal therapeutic algorithm, that clinicians should follow.

PATIENTS AND METHODS

Herein we have conducted a meta-analysis of the current reports dealing with the therapeutic approach of BCOR rearranged sarcomas.

RESULTS

Meta-analysis of the 57 eligible cases from 10 studies resulted to similar Incidence Rate Ratio (IRR) and overall survival (OS) for patients who received Ewing protocols and non-Ewing oriented treatment. Further similar death rate was reported for both strategies (non-Ewing 20% Vs Ewing 21.8%).

CONCLUSION

Our data support that non-Ewing treatment strategy can be considered a safe option, being at least equal to Ewing protocols. The current study provides a hint toward the optimal therapeutic approach of BCOR rearranged sarcomas. Further, the present study challenges the use of the term Ewing-like sarcomas, since the current literature supports that BCOR rearranged sarcomas deserve their own distinct classification in terms of genetics, pathology and therapy.

Small-cell lung cancer

Small-cell lung cancer (SCLC) represents about 15% of all lung cancers and is marked by an exceptionally high proliferative rate, strong predilection for early metastasis and poor prognosis. SCLC is strongly associated with exposure to tobacco carcinogens. Most patients have metastatic disease at diagnosis, with only one-third having earlier-stage disease that is amenable to potentially curative multimodality therapy. Genomic profiling of SCLC reveals extensive chromosomal rearrangements and a high mutation burden, almost always including functional inactivation of the tumour suppressor genes TP53 and RB1. Analyses of both human SCLC and murine models have defined subtypes of disease based on the relative expression of dominant transcriptional regulators and have also revealed substantial intratumoural heterogeneity. Aspects of this heterogeneity have been implicated in tumour evolution, metastasis and acquired therapeutic resistance. Although clinical progress in SCLC treatment has been notoriously slow, a better understanding of the biology of disease has uncovered novel vulnerabilities that might be amenable to targeted therapeutic approaches. The recent introduction of immune checkpoint blockade into the treatment of patients with SCLC is offering new hope, with a small subset of patients deriving prolonged benefit. Strategies to direct targeted therapies to those patients who are most likely to respond and to extend the durable benefit of effective antitumour immunity to a greater fraction of patients are urgently needed and are now being actively explored.

Fusion genes as biomarkers in pediatric cancers: A review of the current state and applicability in diagnostics and personalized therapy

The incidence of pediatric cancers is rising steadily across the world, along with the challenges in understanding the molecular mechanisms and devising effective therapeutic strategies. Pediatric cancers are presented with diverse molecular characteristics and more distinct subtypes when compared to adult cancers. Recent studies on the genomic landscape of pediatric cancers using next-generation sequencing (NGS) approaches have redefined this field by providing better subtype characterization and novel actionable targets. Since early identification and personalized treatment strategies influence therapeutic outcomes, survival, and quality of life in pediatric cancer patients, the quest for actionable biomarkers is of great value in this field. Fusion genes that are prevalent and recurrent in several pediatric cancers are ideally suited in this context due to their disease-specific occurrence. In this review, we explore the current status of fusion genes in pediatric cancer subtypes and their use as biomarkers for diagnosis and personalized therapy. We discuss the technological advancements made in recent years in NGS sequencing and their impact on fusion detection algorithms that have revolutionized this field. Finally, we also discuss the advantages of pairing liquid biopsy protocols for fusion detection and their eventual use in diagnosis and treatment monitoring.

[Malignant round cell tumors : The Ewing sarcoma and beyond]

Ewing sarcomas are highly malignant tumors that are mainly found in children and adolescents. In addition to early clinical diagnosis, correct histopathological and molecular genetic classification is the most important step. Although EWSR1-FLI1 fusion is by far the most common detectable change, there are also other representatives of the Ewing sarcoma family that cannot be distinguished histopathologically and immunohistochemically from classical Ewing sarcomas and that have different molecular genetic profiles. Although a precise molecular genetic differentiation of the various representatives of small round blue cell tumors does not yet lead to any change in the standard chemotherapy and surgical treatment applied, it does allow an estimation of the prognosis and will probably contribute in the future to an even more individualized treatment of Ewing sarcomas within the framework of personalized medicine.

Management of Ewing Sarcoma Family of Tumors: A Short Description of a Rare Primitive Uterine pPNET and Literature Review

Purpose

To describe the outcome of a patient with a rare primitive uterine pPNET and to perform a review of the available data in literature, leading the clinicians to better face this rare disease.

Methods

We have rescued data regarding the multidisciplinary treatment of pPNET from the PUBMED database, highlighting also issues regarding the pathogenesis and the genetic landscape of the ESFTs (Ewing Sarcoma Family of Tumors).

Results

Ewing sarcoma and primitive neuroectodermal tumors (PNETs) are small round cell tumors presenting with different degrees of neuroectodermal differentiation. PNETs are further divided into central PNET and peripheral PNET (pPNET). Since pPNETs share the same genetic background of Ewing Sarcomas, they are considered to belong to the Ewing Sarcoma Family of Tumors (ESFTs). Multimodality treatment currently represents the best choice to offer to the affected patients.

Conclusion

Although pPNETs are generally diagnosed in children and young adults, an elderly woman aged 85 years came to our attention after a diagnosis of uterine pPNET. Her medical history is presented here, along with a literature review of the subject, highlighting the main biological, pathological and clinical features, with a hypothesis about the possible future therapeutic approaches for these rare malignancies.

Undifferentiated round cell sarcomas with CIC-DUX4 gene fusion: expanding the clinical spectrum

Round cell sarcomas are a heterogeneous group of mesenchymal neoplasms with overlapping morphology and immunohistochemical profile. Ewing sarcoma is the most well-known tumour in this group characterised by EWSR1/FUS rearrangements with members of the ETS family of transcription factors. Undifferentiated round cell sarcomas lacking these rearrangements, known as 'Ewing-like' sarcomas, usually show atypical clinical presentation and focal CD99 positivity. This group of tumours can be subdivided into: capicua transcriptional repressor (CIC)-rearranged sarcomas, Bcl6 corepressor (BCOR)-rearranged sarcomas, sarcomas with EWSR1 fusion to non-ETS family members and unclassified round cell sarcomas. We describe seven new cases of CIC-DUX4 rearranged sarcomas with their clinicopathological features, two of which presented in unusual locations (skin and lymph node). Patient age ranged between 23 and 54 years, three of whom were female. In five cases, aggressive behaviour was observed with rapid disease progression and lethal outcome within 15 months. One patient achieved a complete response after chemotherapy. The last patient whose tumour was located purely in the dermis demonstrated no residual tumour in the re-resection specimen, was not given any further treatment and showed no sign of disease after 24 months. Immunohistochemically, tumour cells in all cases showed focal membranous CD99 positivity, while WT1 N-/C-terminus were positive in all 5/5 cases (nuclear and/or cytoplasmic). NGS analysis revealed a CIC-DUX4 fusion in all cases. This study expands the spectrum of anatomical locations of CIC-DUX4 rearranged sarcomas, highlighting the inclusion of this rare entity in the differential diagnosis of undifferentiated tumours in various anatomical locations outside of soft tissues.

3D Tissue-Engineered Tumor Model for Ewing's Sarcoma That Incorporates Bone-like ECM and Mineralization

The tumor microenvironment harbors essential components required for cancer progression including biochemical signals and mechanical cues. To study the effects of microenvironmental elements on Ewing's sarcoma (ES) pathogenesis, we tissue-engineered an acellular three-dimensional (3D) bone tumor niche from electrospun poly(ε-caprolactone) (PCL) scaffolds that incorporate bone-like architecture, extracellular matrix (ECM), and mineralization. PCL-ECM constructs were generated by decellularizing PCL scaffolds harboring cultures of osteogenic human mesenchymal stem cells. The PCL-ECM constructs simulated in vivo-like tumor architecture and increased the proliferation of ES cells compared to PCL scaffolds alone. Compared to monolayer controls, 3D environments facilitated the downregulation of the canonical insulin-like growth factor 1 receptor (IGF-1R) signal cascade through mechanistic target of rapamycin (mTOR), both of which are targets of recent clinical trials. In addition to the downregulation of canonical IGF-1R signaling, 3D environments promoted a reduction in the clathrin-dependent nuclear localization and transcriptional activity of IGF-1R. In vitro drug testing revealed that 3D environments generated cell phenotypes that were resistant to mTOR inhibition and chemotherapy. Our versatile PCL-ECM constructs allow for the investigation of the roles of various microenvironmental elements in ES tumor growth, cancer cell morphology, and induction of resistant cell phenotypes.

PET-CT imaging features that differentiate between positive and negative EWSR1 translocation in Ewing sarcoma

OBJECTIVES

Ewing sarcoma breakpoint region 1 (EWSR1) translocation-negative tumors represent a minor portion of small round cell tumors consistent with Ewing sarcoma morphology. The purpose of this study was to differentiate EWSR1 translocation-positive tumors from EWSR1 translocation-negative tumors using PET-computed tomography features.

MATERIALS AND METHODS

In this retrospective study 27, Ewing sarcoma patients (December 2011 to November 2016) were divided into two groups, EWSR1 translocation-positive and EWSR1 translocation-negative based on cytogenetic analysis. Pretreatment standardized uptake value maximum (SUVmax) and Hounsfield Units (HU) were measured in the primary tumor in the axial slice with the largest tumor diameter.The associations between SUVmax, HU and the presence of EWSR1 translocation were evaluated. Receiver operating characteristic curve analysis was used to determine cut-off levels of SUVmax and HU suggestive of EWSR1-negative tumors.

RESULTS

Twenty-one patients were classified as EWSR1-positive and six as EWSR1-negative. Eighteen had SUVmax and 21 had HU measurements. EWSR1-negative tumors had significantly higher SUVmax values (P = 0.003) and significantly lower HU values (P = 0.008). Receiver operating characteristic curve analysis showed that SUVmax had diagnostic ability to discriminate between EWSR1-negative and EWSR1-positive tumors (area under the curve = 0.964, P = 0.006). A SUVmax of at least 10 had a sensitivity of 100% and specificity of 85.7% for EWSR1-negative tumors. HU had lower diagnostic ability than SUVmax (area under the curve = 0.881, P = 0.012). A HU up to 57 had a sensitivity of 81.3% and specificity of 80.0% for EWSR1-negative tumors.

CONCLUSION

Higher SUVmax and lower HU may differentiate between EWSR1-positive and EWSR1-negative tumors. This may reflect EWSR1-negative tumor aggressiveness.

EWSR1-NFATC2 and FUS-NFATC2 Gene Fusion-Associated Mesenchymal Tumors: Clinicopathologic Correlation and Literature Review

The spectrum of mesenchymal tumors associated with rearrangements of the EWSR1 gene has been growing in recent years due to progress in molecular detection techniques. Originally identified as the gene involved in the pathogenesis of Ewing sarcoma, the EWSR1 gene is now known to be rearranged in diverse clinical and histopathological entities. The NFATC2 gene is one of the many translocation partners of EWSR1 in gene fusions in a morphologically typical, albeit rare, subgroup of mesenchymal tumors. Little is known about the clinical characteristics of tumors containing NFATC2 gene rearrangements since most of the few reports published describe molecular rather than clinical aspects. In the current study, we report three patients with tumors carrying the EWSR1-NFATC2 gene translocation, including one rare primary tumor of soft tissues. Another patient with a benign-appearing bone tumor with a unique FUS-NFATC2 gene translocation is described. In various mesenchymal tumors (e.g., myxoid/round cell liposarcoma, low-grade fibromyxoid sarcoma, or angiomatoid fibrous histiocytoma), the FUS gene, as a member of the TET family, may be alternatively rearranged instead of the EWSR1 gene without any noticeable influence on the microscopical appearance or clinical outcome. This fact seems not to apply to mesenchymal tumors with the involvement of the NFATC2 gene because both in our experience and according to the extensive literature review, they have different properties on the morphological and molecular level. Both ESWSR1-NFATC2 and FUS-NFATC2 fusion-carrying tumors do not show microscopical or clinical features of Ewing sarcoma.

Ewing-like sarcoma: An emerging family of round cell sarcomas

Ewing-like sarcomas are an emerging subgroup of small round blue cell sarcomas that share various degrees of morphological, immunohistochemical, molecular, and clinical similarity with Ewing sarcoma. Despite these similarities, Ewing-like sarcomas lack the pathognomonic molecular hallmark of Ewing sarcoma: A translocation between a gene of the RNA-binding TET family (EWSR1 or FUS) with a gene of the ETS-transcription family ( FLI1, ERG, ETV1, ETV4, or FEV). Recently, increased use of modern molecular methods based on next-generation sequencing have enabled the identification of distinct subgroups within this previously uncharacterized group of Ewing-like sarcomas based on the discovery of novel molecular driving events. The focus of this review is to provide an update on the main subcategories of Ewing-like sarcomas discovered to date: CIC-rearranged sarcomas, BCOR-rearranged sarcomas, sarcomas with a rearrangement between EWSR1 and a non-ETS family gene, and the substantial fraction of tumors which remain uncharacterized by molecular methods. There is increasing evidence that these tumors represent stand-alone entities with unique characteristics rather than simply a subgroup of Ewing sarcoma; thus, the question of the best therapeutic approach for these often aggressive sarcomas remains of primary importance. Ultimately, large collaborative efforts will be necessary to better determine the characteristics of this rare, heterogeneous family of tumors.

[Ewing sarcomas and Ewing-like sarcomas : New aspects]

Sarcomas of the Ewing family of tumors are aggressive neoplasms occurring in bone and soft tissue of mostly children and young adults. Classical Ewing sarcomas are pathognomonically characterized by fusions between a gene of the RNA-binding TET family (EWSR1 or FUS) with a gene of the ETS-transcription family (FLI1, ERG, ETV1, ETV4 or FEV). Less frequent cases designated as Ewing-like sarcomas show different genetic rearrangements between EWSR1 and non-ETS genes (NFATC2, POU5F1, SMARCA5, PATZ, ZSG, SP3). Moreover, new molecular alterations biologically unrelated to Ewing sarcomas have recently been described in the category of undifferentiated round cell sarcomas including CIC-DUX4 fusions or BCOR alterations, each carrying unique gene expression signatures. In contrast to classical Ewing sarcomas, the morphologic spectrum of these tumor entities is much broader and includes round cell areas as well as spindled and myxoid components. The immunohistochemical profile with inconsistent CD99 positivity makes diagnosis more difficult and requires the use of a broad spectrum of antibodies and elaborate molecular work-up. Further studies for future therapeutic decision making in these newly described round cell sarcomas as well as for molecular subclassification of undifferentiated round cell sarcomas are ongoing.

Rhabdomyosarcoma, Ewing Sarcoma, and Other Round Cell Sarcomas

Several recent advances have been made in the diagnosis and therapy of malignant small round cell tumors that affect children, particularly in rhabdomyosarcoma, Ewing sarcoma, and other round cell sarcomas. These advances have provided new insights into the pathologic, histologic, and genomic characterization of specific tumor subtypes, which has led to the identification of novel therapeutic targets and improved stratification of risk. This has, in turn, led to improved efficacy in clinical trials of new drug combinations, thereby increasing the survival of patients with newly diagnosed and refractory or recurrent round cell sarcomas. Here, we review the progress that has been made using genomics to identify novel pathologic genomic rearrangements, as well as therapeutic targets. We also describe how clinical and molecular factors have helped refine risk stratification and therapies that have led to improved clinical outcomes in patients with round cell sarcomas.

Results for patients with sarcoma not otherwise specified and other diagnoses than Ewing sarcoma treated according to the Euro-EWING 99 trial

BACKGROUND

Euro-EWING 99 trial of the European Ewing tumor Working Initiative of National Groups (EE99) was an international phase III study in patients with Ewing sarcoma. The German Society of Pediatric Oncology and Hematology (GPOH) data center registered and followed patients with other diagnoses than Ewing sarcoma who were treated according to the EE99 protocol in an additional non-Ewing database.

PROCEDURE

Data of 27 patients with other diagnoses than Ewing sarcoma treated according to the EE99 protocol were analyzed. Patients had miscellaneous histologic diagnoses, the majority were diagnosed with sarcoma not otherwise specified (NOS) arising in bone and soft tissue (63%).

RESULTS

The median age at diagnosis was 16.9 years (range 4.5-41.4). Localized disease was diagnosed in 61.5% of the patients and 38.5% had distant metastases at time of primary diagnosis. The median follow-up time was 3.7 years (range 0.5-9.5). Patients with localized disease showed a 3-year event-free survival (EFS) of 68%, compared to 3-year EFS of 20% in patients with metastases (P = 0.042). Three-year EFS for patients with sarcoma NOS was 52%, patients with localized and metastatic disease showed 3-year EFS of 66 and 20%, respectively.

CONCLUSION

EFS in patients with other diagnoses than Ewing sarcoma treated according to EE99 was significantly higher in patients with localized than metastatic disease. Sarcomas of soft tissue and bone that cannot be classified to current diagnostic categories constitute a therapeutic challenge.

DUX4 Immunohistochemistry Is a Highly Sensitive and Specific Marker for CIC-DUX4 Fusion-positive Round Cell Tumor

The histologic differential diagnosis of pediatric and adult round cell tumors is vast and includes the recently recognized entity CIC-DUX4 fusion-positive round cell tumor. The diagnosis of CIC-DUX4 tumor can be suggested by light microscopic and immunohistochemical features, but currently, definitive diagnosis requires ancillary genetic testing such as conventional karyotyping, fluorescence in situ hybridization, or molecular methods. We sought to determine whether DUX4 expression would serve as a fusion-specific immunohistochemical marker distinguishing CIC-DUX4 tumor from potential histologic mimics. A cohort of CIC-DUX4 fusion-positive round cell tumors harboring t(4;19)(q35;q13) and t(10;19)(q26;q13) translocations was designed, with additional inclusion of a case with a translocation confirmed to involve the CIC gene without delineation of the partner. Round cell tumors with potentially overlapping histologic features were also collected. Staining with a monoclonal antibody raised against the C-terminus of the DUX4 protein was applied to all cases. DUX4 immunohistochemistry exhibited diffuse, crisp, strong nuclear staining in all CIC-DUX4 fusion-positive round cell tumors (5/5, 100% sensitivity), and exhibited negative staining in nuclei of all of the other tested round cell tumors, including 20 Ewing sarcomas, 1 Ewing-like sarcoma, 11 alveolar rhabdomyosarcomas, 9 embryonal rhabdomyosarcomas, 12 synovial sarcomas, 7 desmoplastic small round cell tumors, 3 malignant rhabdoid tumors, 9 neuroblastomas, and 4 clear cell sarcomas (0/76, 100% specificity). Thus, in our experience, DUX4 immunostaining distinguishes CIC-DUX4 tumors from other round cell mimics. We recommend its use when CIC-DUX4 fusion-positive round cell tumor enters the histologic differential diagnosis.

BCOR-CCNB3 Undifferentiated Sarcoma-Does Immunohistochemistry Help in the Identification?

Recent methodology has enabled the identification of some new genetic subgroups within the melting pot of lesions presently classified by the 2013 WHO classification as "undifferentiated/unclassified sarcomas". One of these subgroups is characterized by a paracentric inversion of the X chromosome with consequent formation of a BCOR-CCNB3 fusion. Clinical and pathological features of these tumors overlap with the Ewing sarcoma family as well as other soft tissue sarcomas, thus making them difficult to diagnose. To investigate the morphological and immunohistochemical characteristics of BCOR-CCNB3 positive sarcoma, we reviewed two sarcoma series, comprising 632 and 121 cases. The 11 tumors harboring the BCOR-CCNB3 fusion, identified by CCNB3 immunohistochemistry and/or RT-PCR, were reevaluated for morphological characteristics and further immunohistochemical investigations for CCNB3, SATB2, and Pax8 were performed. Tumors harboring a BCOR-CCNB3 fusion (11/753) occured exclusively in males, with a mean age at diagnosis of 12.9 years, and were mainly axially located. In this group of either spindled or round cell tumors, vesicular nuclei with finely dispersed chromatin, inconspicuous nucleoli and an arciform vascular pattern were pathognomonic. More than 50% of cases stained positive for SATB2 and Pax8, raising the hypothesis of a potential use of these markers in the identification of BCOR-CCNB3 positive undifferentiated/unclassified sarcomas. CCNB3 was confirmed as a useful ancillary immunohistochemical marker.

Primary CIC-DUX4 round cell sarcoma of the kidney: A treatment-refractory tumor with poor outcome

The CIC-DUX4 sarcoma is a subset of the undifferentiated small round cell sarcoma family, presently recognized as a new clinicopathological entity. It is a rare and highly aggressive tumor usually arising in the soft parts of the limbs and the trunk. Only a very few cases of primitive visceral CIC-DUX4 have been hitherto described. We report the case of a 29 year-old male patient with a primary CIC-DUX4 sarcoma of the kidney with lung metastasis. The outcome of the disease was rapidly unfavorable. Despite radical nephrectomy, the patient experienced an early local retroperitoneal recurrence associated with lung and liver metastases. The tumor did not respond to four successive lines of chemotherapy nor to palliative radiotherapy. Due to partial morphologic and immunohistochemical overlap with Ewing sarcoma, CIC-DUX4 positive tumors have generally been considered as Ewing-like sarcomas and managed similarly. However, this tumor shows a high propensity to metastasize and is much less sensitive to chemotherapy than Ewing sarcomas. The management of this type of very aggressive sarcoma needs to be defined by comprehensive biological and clinical studies.

Evaluation of ETV4 and WT1 expression in CIC-rearranged sarcomas and histologic mimics

A distinct subset of round cell sarcomas harbors capicua transcriptional repressor (CIC) rearrangement. Diagnosing these sarcomas can be difficult owing to their resemblance to Ewing sarcoma and other 'small round blue cell tumors'; molecular techniques are generally required. Recent gene expression studies of CIC-rearranged sarcomas identified the upregulation of ETV4. We assessed the sensitivity and specificity of ETV4 and WT1 immunohistochemistry for CIC-rearranged sarcoma. We evaluated whole-tissue sections from 40 CIC-rearranged sarcomas, 40 Ewing sarcomas, 4 BCOR-CCNB3 sarcomas, 6 unclassified round cell sarcomas, and 150 histologic mimics. Moderate-to-strong nuclear immunoreactivity for ETV4 in at least 50% of cells was observed in 36 (90%) CIC-rearranged sarcomas and 10 (5%) other tumors, including 5 unclassified round cell sarcomas, 2 Wilms tumors, and 1 each desmoplastic small round cell tumor, melanoma, and small cell carcinoma. Thirty-eight (95%) CIC-rearranged sarcomas showed nuclear staining for WT1, and 34 (85%) were positive for both ETV4 and WT1. Of 182 other tumors evaluated, 34 (19%) showed nuclear WT1 positivity, including all Wilms tumors and desmoplastic small round cell tumors, 5 unclassified round cell sarcomas, and a subset of lymphoblastic lymphomas, rhabdomyosarcomas, mesenchymal chondrosarcomas, carcinomas, and melanomas. In summary, diffuse moderate-to-strong ETV4 expression is present in most CIC-rearranged sarcomas and unclassified round cell sarcomas. More limited expression is seen in small subsets of various other round cell neoplasms. Nuclear WT1 expression is also present in most CIC-rearranged sarcomas and unclassified round cell sarcomas, along with Wilms tumors and desmoplastic small round cell tumors, and subsets of various histologic mimics. The sensitivity and specificity of diffuse ETV4 expression for CIC-rearranged sarcomas are 90% and 95%, respectively, whereas the sensitivity and specificity of WT1 are 95% and 81%, respectively. Diffuse ETV4 along with at least focal WT1 expression is helpful to distinguish CIC-rearranged sarcoma from Ewing sarcoma and other histologic mimics.

Osteosarcoma With Apparent Ewing Sarcoma Gene Rearrangement

Poorly differentiated round cell sarcomas present diagnostic challenges because of their variable morphology and lack of specific immunophenotypic markers. We present a case of a 15-year-old female with a tibial tumor that exhibited features of Ewing-like sarcoma, including apparent rearrangement of the EWSR1 gene. Hybridization capture-based next-generation DNA sequencing showed evidence of complex genomic rearrangements, absence of known pathogenic Ewing-like chromosome translocations, and deletions RB1, PTCH1, and ATRX, supporting the diagnosis of osteosarcoma. This illustrates the potential of clinical genomic profiling to improve diagnosis and enable specifically targeted therapies for cancers with complex pathologies.

CIC-DUX4 fusion-positive round-cell sarcomas of soft tissue and bone: a single-institution morphological and molecular analysis of seven cases

AIMS

Round-cell sarcomas lacking specific translocations represent a diagnostic challenge. The aim of this study was to describe seven cases of CIC-DUX4 fusion-positive sarcomas, including the first reported example arising primarily in bone.

METHODS AND RESULTS

Patients ranged in age from 15 years to 44 years (median: 33 years). Six cases arose from the soft tissues, and one from the iliac bone. Morphologically, all cases showed an undifferentiated round-cell population with greater atypia and pleomorphism than Ewing sarcoma. Immunohistochemically, all tumours showed focal and weak positivity for CD99, and five of seven showed nuclear and/or cytoplasmic positivity for Wilms tumour 1. Five patients had lung metastases at presentation. All patients received chemotherapy according to Ewing sarcoma protocols. All but one patient (the one with a bone tumour) died of disease after a mean of 14.5 months from the diagnosis (range: 8-20 months).

CONCLUSIONS

Our series confirms that CIC-DUX4 fusion-positive sarcomas are aggressive tumours with an adverse prognosis, and with clinical, histological and genetic differences from Ewing sarcoma. The best therapeutic approach needs to be investigated.

Selected Diagnostically Challenging Pediatric Soft Tissue Tumors

Many benign and malignant soft tissue tumors in children are challenging and their diagnosis requires knowledge of their vast diversity, histopathological complexity, and immunohistochemical, cytogenetic, and molecular characteristics. The importance of clinical and imaging features cannot be overstated. Soft tissue sarcomas account for 15% of all pediatric malignancies after leukemia/lymphoma, central nervous system tumors, neuroblastoma and Wilms tumor. This article discusses selected challenging pediatric soft tissue tumors with an update on recently described entities.

Monosomy 22 and partial loss of INI1 expression in a biphasic synovial sarcoma with an Ewing sarcoma-like poorly differentiated component: Report of a case

Poorly differentiated synovial sarcoma (PDSS) is a less common subtype of synovial sarcoma (SS) associated with a poor prognosis. We present a case of a SS with a poorly differentiated component that resembles Ewing sarcoma (ES). Initial immunohistochemical staining revealed a characteristic and strong expression of transducin-like enhancer of split 1 (TLE1) and weak to absent expression of integrase integrator 1 (INI1) staining. Stainings for keratin and epithelial membrane antigen (EMA) were negative in the tumoral lesion. Fluorescence In Situ Hybridization (FISH) analysis showed a rearrangement of the synaptotagmin (SYT) gene, confirming the diagnosis of SS. FISH analysis for the EWS RNA-binding protein 1 (EWSR1) gene revealed monoallelic loss of EWSR1. This finding was confirmed by an array comparative genomic hybridization (aCGH), showing complete loss of chromosome 22. Based on literature review, showing only a handful of cases of cytogenetically studied SS with loss of chromosome 22, this is probably a rare event in SS. Therefore, we assume that monoallelic loss of chromosome 22 cannot fully elaborate the underlying mechanism of the INI1 staining pattern in all SS, but it could account for the weak to absent INI1 staining in at least some cases.

Defining Ewing and Ewing-like small round cell tumors (SRCT): The need for molecular techniques in their categorization and differential diagnosis. A study of 200 cases

BACKGROUND

Differentiation of Ewing sarcoma family of tumors (ESFT) and Ewing-like tumors remains problematic. Certain ESFT with morphological and immunohistochemical (IHC) profiles lack the EWSR1-ETS transcript. To improve diagnostic accuracy we investigated the presence of several specific transcripts in 200 small round cell tumors (SRCT) displaying ESFT morphology and immunophenotype in which EWSR1 FISH analysis was non-informative or negative.

DESIGN

200 tumors (formalin-fixed, paraffin-embedded) were analyzed by RT-PCR. All tumors were tested for EWSR1-ETS, EWSR1/WT1, PAX3/7-FOX01 or SYT/SSX transcripts, and the negative tumors were subsequently analyzed for CIC/DUX4, BCOR/CCNB3 and CIC/FOX04 transcripts.

RESULTS

133 (66.5%) ESFT displayed one of the above EWSR1-ETS translocations. Three cases (1.5%) revealed the SYT-SSX transcript for Synovial sarcoma, and one (0.5%) a EWSR1-WT1 transcript for Desmoplastic Small Round Cell tumor. The CIC-DUX4 translocation was found in six Ewing-like tumors (3%) with CD99 positivity. The BCOR-CCNB3 gene fusion was observed in 5 tumors (2.5%) displaying round or spindle cells with strong CCNB3 IHC expression in 3 tumors. Moreover, RT-PCR failed to detect any gene fusion transcripts in 19 tumors (9.5%) and were considered "undifferentiated small round cell sarcoma" (SRCS). Molecular biology results were non-informative in 33 SRCTs (16.5%) due to RNA degradation through inadequate fixation and/or decalcification.

CONCLUSION

Our analysis of 200 SRCTs confirms the molecular heterogeneity of neoplasms with ESFT morphology and highlight that molecular studies with RT-PCR including new emerging gene fusion transcripts are mandatory for the diagnosis when EWSR1 FISH is negative or non-informative. The incidence of CIC-DUX4, BCOR-CCNB3 and CIC-FOX04 transcripts was relatively low. A small group of Ewing-like sarcomas or undifferentiated SRCS remains unclassified. Adopting appropriate tissue fixation and processing protocols is important to avoid degradation of fixed/embedded tissue when no frozen tumor is available.

The Evolution of Pediatric Soft Tissue Sarcoma Classification in the Last 50 Years

This review discusses the history of the classification of soft tissue sarcomas in children and adolescents, the current transition toward integration of morphology and molecular genetics as new entities emerge, and future perspectives.

Immunohistochemical Markers of Soft Tissue Tumors: Pathologic Diagnosis, Genetic Contributions, and Therapeutic Options

After ~30 years of widespread usage, immunohistochemistry (IHC) has become a standard method of diagnosis for surgical pathology. Because of the plethora of diagnoses and often subtle nature of diagnostic criteria, IHC finds particular utility in soft tissue tumors. The use of progressively small amounts of tissue for diagnosis highlights the importance of this method. The sensitivity and crispness of IHC stains have progressively improved with the advent of new techniques. Traditionally, IHC detects cell-typic markers that characterize cell phenotypes, such as chromogranin for neuroectodermal tissue, myogenin for skeletal muscle, and cytokeratin for epithelium. However, the advent of genetic discoveries have led to IHC testing for detection of fusion gene products or overexpressed oncogenes associated with deletions and mutations. Proliferation-based markers such as Ki-67 can also be used for prognosis and grading, but more standardization is needed. Development of monoclonal antibody-based pharmaceuticals, such as imatinib or crizotinib, holds the promise of tailored anticancer therapy. IHC thus has assumed importance not only for diagnosis but also for guidance of personalized medicine.

Pilot Trial of FANG Immunotherapy in Ewing's Sarcoma

We report on 12 consecutive patients with advanced/metastatic Ewing's sarcoma who were treated as a separate cohort of a phase 1 trial of FANG autologous immunotherapy (1 × 10(6)-2.5 × 10(7) cells/intradermal injection each month for minimum 4 months). Safety and clinical response were monitored. Patient immune response to unmodified autologous tumor cells was assessed by gamma interferon-enzyme-linked immunospot (γIFN-ELISPOT) assay using peripheral blood mononuclear cells from baseline (pretreatment) and multiple postvaccination time points. None of the 12 patients (47 vaccinations) developed grade 2/3/4 drug-related toxicity. Median product release granulocyte-macrophage colony-stimulating factor expression was 1,941 pg/10(6) cells, and TGFβ1and TGFβ2 knockdown were 99 and 100%, respectively. Eight patients were assessed for ELISPOT response to autologous tumor cells at baseline and all (100%) were negative. In contrast, follow-up ELISPOT response at month 1 or month 4 (one patient) after FANG was positive in all eight patients. One patient achieved a partial tumor response (38% tumor reduction, RECIST 1.1). The Kaplan-Meier estimated survival of these 12 patients at 1 year was 75%. In this phase 1 study in patients with Ewing's sarcoma, FANG immunotherapy was well tolerated, elicited a tumor-specific systemic immune response in all patients, and was associated with favorable 1-year survival. Further clinical testing is indicated.

Molecular diagnostics in soft tissue sarcomas and gastrointestinal stromal tumors

Soft tissue sarcomas are rare malignant heterogenous tumors of mesenchymal origin with over fifty subtypes. The use of hematoxylin and eosin stained sections (and immunohistochemistry) in the morphologic assessment of these tumors has been the bane of clinical diagnosis until recently. The last decade has witnessed considerable progress in the understanding and application of molecular techniques in refining the current understanding of soft tissue sarcomas and gastrointestinal stromal tumors beyond the limits of traditional approaches. Indeed, the identification of reciprocal chromosomal translocations and fusion genes in some subsets of sarcomas with potential implications in the pathogenesis, diagnosis and treatment has been revolutionary. The era of molecular targeted therapy presents a platform that continues to drive biomarker discovery and personalized medicine in soft tissue sarcomas and gastrointestinal stromal tumors. In this review, we highlight how the different molecular techniques have enhanced the diagnosis of these tumors with prognostic and therapeutic implications.

Gene Expression Profiling of Ewing Sarcoma Tumors Reveals the Prognostic Importance of Tumor-Stromal Interactions: A Report from the Children's Oncology Group

Relapse of Ewing sarcoma (ES) can occur months or years after initial remission, and salvage therapy for relapsed disease is usually ineffective. Thus, there is great need to develop biomarkers that can predict which patients are at risk for relapse so that therapy and post‐therapy evaluation can be adjusted accordingly. For this study, we performed whole genome expression profiling on two independent cohorts of clinically annotated ES tumours in an effort to identify and validate prognostic gene signatures. ES specimens were obtained from the Children's Oncology Group and whole genome expression profiling performed using Affymetrix Human Exon 1.0 ST arrays. Lists of differentially expressed genes between survivors and non‐survivors were used to identify prognostic gene signatures. An independent cohort of tumours from the Euro‐Ewing cooperative group was similarly analysed as a validation cohort. Unsupervised clustering of gene expression data failed to segregate tumours based on outcome. Supervised analysis of survivors versus non‐survivors revealed a small number of differentially expressed genes and several statistically significant gene signatures. Gene‐specific enrichment analysis demonstrated that integrin and chemokine genes were associated with survival in tumours where stromal contamination was present. Tumours that did not harbour stromal contamination showed no association of any genes or pathways with clinical outcome. Our results reflect the challenges of performing RNA‐based assays on archived bone tumour specimens. In addition, they reveal a key role for tumour stroma in determining ES prognosis. Future biological and clinical investigations should focus on elucidating the contribution of tumour:micro‐environment interactions on ES progression and response to therapy.