Undifferentiated Round Cell Sarcomas Research Articles

Clinicopathological and molecular features of small round cell sarcoma of bone and soft tissue: a study of 72 cases

Objective: To investigate the clinicopathological, immunohistochemical and molecular features of small round cell sarcoma (SRCS) of the bone and soft tissue, and to compare the diagnostic value of different techniques. Methods: Seventy-two cases of SRCS of the bone and soft tissue diagnosed at People's Hospital, Peking University from January 2016 to March 2020 were recruited and retrospectively analyzed for pathological morphology, immunophenotype and fluorescence in situ hybridization (FISH) data. Next generation sequencing (NGS) was performed on 13 difficult cases. Results: In the study cohort, the patients ranged in age from 4-55 years, with a male predominance. The most Ewing's sarcomas and osteosarcomas occurred in the bone, while CIC-rearranged sarcomas, BCOR-rearranged sarcoma, synovial sarcoma, extraskeletal myxoid chondrosarcoma and FUS-NFATc2 rearranged sarcoma occurred in soft tissue. Histologically, all cases were composed predominantly of small round cells. Most cases were positive for vimentin and CD99, and showed a variable reactivity for neurogenic markers. Muscle marker and epithelial marker were negative for most cases. Combined with clinical features, histopathologic findings, immunophenotype, FISH and NGS, we diagnosed 46 Ewing sarcomas, 14 osteosarcomas, 3 CIC-rearranged sarcomas, 1 BCOR-rearranged sarcoma, 1 synovial sarcoma, 1 clear cell soft tissue sarcoma, 1 extraskeletal myxoid chondrosarcoma, 1 FUS-NFATc2 rearranged sarcoma, and 4 undifferentiated small round cell sarcomas. Conclusions: SRCS of bone and soft tissue is a group of malignant mesenchymal tumors based on morphological features. Most cases can be diagnosed with a combination of clinical characteristics, morphological features and immunohistochemical phenotype, while some cases require such further tests as FISH and NGS technologies, and NGS can be useful in diagnosing and categorizing SRCS.

Pathological fracture in paediatric bone tumours and tumour-like lesions: A predictor of benign lesions?

To determine the incidence and causes of pathological fractures in paediatric bone tumours and tumour-like lesions, and to determine if they are predictive of benign lesions. Retrospective review of children with suspected bone tumours referred to a specialist musculoskeletal oncology service between September 2019 and August 2020. Data recorded included patient age and gender, lesion location, the presence of a pathological fracture on the initial plain radiograph, and the final diagnosis made either by image-guided biopsy/curettage or based on typical imaging features. 231 patients were included with 233 lesions (138 males and 93 females with mean age 10.5 years, range 3 months-18 years). Final diagnosis was based on histology in 85 (36.5%) cases and imaging in 148 (63.5%) cases, 52 (22.3%) lesions classed as non-neoplastic, 139 (59.7%) as benign and 42 (18%) as malignant. Pathological fractures were seen in 41 cases (17.6%) at presentation, involving the humerus in 19 (46.3%), the femur in 14 (34.1%), the tibia in 3 (7.3%), the fibula and radius in two each (4.9%) and the second toe proximal phalanx in 1 (2.4%) (p < 0.001). The commonest underlying lesions included simple bone cyst (n = 17; 41.5%) and non-ossifying fibroma (n = 10; 24.4%). Only 4 cases (9.75%) were malignant, one case each of osteosarcoma, Ewing sarcoma, leukaemia and BCOR undifferentiated round cell sarcoma. Pathological fracture occurred in 27.7% of non-malignant lesions and 9.5% of malignant lesions, this difference being statistically significant (p < 0.001). Pathological fractures were seen in 17.6% of paediatric bone tumours, tumour-like lesions, being significantly associated with humeral location and non-malignant diagnosis. Demonstrates the frequency, location and underlying diagnosis of pathological fractures in paediatric bone tumour and tumour-like lesions.

Update of pediatric soft tissue tumors with review of conventional MRI appearance-part 2: vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas.

There are numerous soft tissue tumors and tumor-like conditions in the pediatric population. Magnetic resonance imaging is the most useful modality for imaging these lesions. Although certain soft tissue lesions exhibit magnetic resonance features characteristic of a specific diagnosis, most lesions are indeterminate, and a biopsy is necessary for diagnosis. We provide a detailed update of soft tissue tumors and tumor-like conditions that occur in the pediatric population, emphasizing each lesion's conventional magnetic resonance imaging appearance, using the recently released 5th edition of the World Health Organization Classification of Soft Tissue and Bone Tumors as a guide. In part one of this review, pediatric tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors are discussed. In part two, vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas are reviewed. Per the convention of the WHO, these lesions involve the connective, subcutaneous, and other non-parenchymatous organ soft tissues, as well as the peripheral and autonomic nervous system.

Reassessment of EWSR1 gene rearrangement-negative undifferentiated round cell sarcomas in bone and soft tissues by fluorescence in situ hybridization

Objective: To unravel the CIC rearrangement sarcomas and BCOR-CCNB3 sarcomas from EWSR1 rearrangement-negative undifferentiated round cell sarcomas in the bone and soft tissues. Methods: Twenty-eight cases of EWSR1 rearrangement-negative undifferentiated round cell sarcomas of bone and soft tissues, tested for CIC rearrangement and BCOR rearrangement by fluorescence in situ hybridization and related immunostaining were analyzed, and some of the BCOR rearrangement cases were verified by reverse transcription-polymerase chain reaction. Results: Five of 28 (17.9%) tested cases were positive for CIC rearrangement and six (21.4%) for BCOR rearrangement. Histopathologically, CIC rearrangement sarcomas comprised nodular aggregates of round to polygonal cells, containing hyperchromatic nuclei, prominent nucleoli and moderate cytoplasm, with focal variable necrosis and myxoid stroma. BCOR-CCNB3 sarcomas mostly comprised diffusely arranged, round to oval to short spindly cells with angulated nuclei, vesicular chromatin, inconspicuous nucleoli and interspersed vessels. Immunohistochemically, five of six BCOR-CCNB3 sarcomas showed CCNB3 immunostaining, which could be helpful for diagnosis. Two patients with CIC rearrangement sarcoma died of the diseases in seven months and twenty-two months. One patient with BCOR-CCNB3 sarcoma died of the diseases in forty-six months. Conclusions: Overall, 39.3% of the EWSR1 rearrangement-negative undifferentiated round cell sarcomas are CIC rearrangement sarcomas and BCOR-CCNB3 sarcomas. Molecular testing is helpful for diagnosis.

Update of pediatric soft tissue tumors with review of conventional MRI appearance-part 1: tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors.

There are numerous soft tissue tumors and tumor-like conditions in the pediatric population. Magnetic resonance imaging is the most useful modality for imaging these lesions. Although certain soft tissue lesions exhibit magnetic resonance features characteristic of a specific diagnosis, most lesions are indeterminate, and a biopsy is necessary for diagnosis. We provide a detailed update of soft tissue tumors and tumor-like conditions that occur in the pediatric population, emphasizing each lesion's conventional magnetic resonance imaging appearance, using the recently released 5th edition of the World Health Organization Classification of Soft Tissue and Bone Tumors as a guide. In part one of this review, pediatric tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors are discussed. In part two, vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas are reviewed. Per the convention of the WHO, these lesions involve the connective, subcutaneous, and other non-parenchymatous-organ soft tissues, as well as the peripheral and autonomic nervous system.

Detection of BCOR gene rearrangement in Ewing-like sarcoma: an important diagnostic tool

BackgroundBCOR-CCNB3 sarcoma (BCS) is a group of undifferentiated small round cell sarcomas harboring the BCOR gene rearrangement which shares morphology with the Ewing sarcoma family as well as other malignant round blue cell tumors, thus making them difficult to diagnose. The aim of this study was to explore the role of molecular techniques in the diagnosis of BCS.MethodsTwenty-three cases of EWSR1 rearrangement-negative undifferentiated small round cell sarcomas (Ewing-like sarcoma) were analyzed for the presence of BCOR gene rearrangement by Fluorescence in situ hybridization (FISH) and Reverse Transcription -Polymerase Chain Reaction (RT-PCR). The clinicopathological features of the positive cases were also reviewed. Fifteen additional cases were used as negative controls.ResultsEight cases were found with BCOR gene rearrangement by FISH and reappraised as BCS. The patients ranged in age from 8 to 20 years old, with a male predominance (M:F = 6:2). All tumors were located in the lower extremities. The tumor locations were more common in bone (n = 6) than deep soft tissue (n = 2). Histologically, 7 of 8 tumors were predominately composed of spindle or ovoid cells. The tumor cells were usually arranged in solid hypercellular sheets without a distinct architectural pattern. IHC showed expression of TLE1 (100%), CCNB3 (88%), BCOR (71%). RT-PCR for BCOR-CCNB3 fusion transcript was positive in 7 of 8 cases. Pre-operative chemotherapy resulted in eradication of tumors in 5 patients after a follow-up of 7 to 42 months.ConclusionsEfficient diagnosis of BCOR rearranged sarcomas is achieved by the using a combination of FISH and RT-PCR assays.

Molecular, biological and diagnostic features of Ewing sarcoma and undifferentiated small round cell sarcomas of bone and soft tissue

Ewing’s sarcoma is a highly malignant small round cell tumor with a unique rearrangement of the EWSR1 (FUS) gene with partners genes of ETS family. Tumors with Ewing's sarcoma morphological features lacking without specific EWSR1 rear-rangement called undifferentiated small round cell sarcomas of bone and soft tissue. This group includes: sarcomas with СIC gene rearrangement, sarcomas with BCOR gene rearrangement and sarcomas with EWSR1 (FUS) gene rearrangement with non-ETS gene-partner. Clinical, morphological and molecular genetic characteristics of these groups of tumors will be described below

P135 Undifferentiated round cell and spindle cell sarcomas: the current paradigm

IntroductionThe classification of soft tissue and bone neoplasms is experiencing a transformation as methods to detect gene fusions expand. Next-generation sequencing panels, anchored multiplex polymerase chain reaction systems and comprehensive RNA sequencing have all contributed to new histological categorisation. The EWSR1-NFATC2 is one such novel translocation found in a round cell sarcomas. These sarcoma sit within the WHO group of undifferentiated round and spindle cell sarcomas. They presents as either a primary bone or soft tissue tumour and exhibits distinctive histopathologic features.MethodsThis is a case study of a soft tissue mesenchymal tumour with the recently described gene fusion EWSR1-NFATC2. The case is described, with 3-month outcomes and considered in the most recent literature on this sarcoma subset (26 cases).ResultsThis case study prompted a look at the current NHS paradigm for these emerging histopathologically distinctive sarcoma subgroups. At present the expertise with the sarcoma MDT, along with second opinion from other national MDTs is the format for subtype specific sarcoma management, informed by recent literature.ConclusionThe EWSR1-NFATC2 fusion round cell sarcoma tumours are an example of a very recently emerged sarcoma subset which display oncological variance to the wider Ewing’s family. The novel literature guided the Southmead and Royal Marsden MDT opinions to proceed straight to surgical excision.The Authors recommend a national prospective database for rare sarcoma subsets, particularly those that appear to exhibit distinctive clinicopathology characteristics. The format could be through the RSTN collaborative, secure anonymised data collection can be collected through REDCap.

Specific and Sensitive Diagnosis of BCOR-ITD in Various Cancers by Digital PCR.

BCOR is an epigenetic regulator altered by various mechanisms including BCOR-internal tandem duplication (BCOR-ITD) in a wide range of cancers. Six different BCOR-ITD in the 3’-part of the coding sequence of exon 15 have been reported ranging from 89 to 114 bp in length. BCOR-ITD is a common genetic alteration found in clear cell sarcoma of the kidney and primitive myxoid mesenchymal tumor of infancy (PMMTI) and it characterizes a new type of central nervous system tumor: “CNS tumor with BCOR-ITD”. It can also be detected in undifferentiated round cell sarcoma (URCS) and in high-grade endometrial stromal sarcoma (HGESS). Therefore, it is of utmost importance to search for this genetic alteration in these cancers with the most frequent technique being RNA-sequencing. Here, we developed a new droplet PCR assay (dPCR) to detect the six sequences characterizing BCOR-ITD. To achieve this goal, we used a single colored probe to detect both the duplicated region and the normal sequence that acts as a reference. We first generated seven synthetic DNA sequences: ITD0 (the normal sequence) and ITD1 to ITD6 (the duplicated sequences described in the literature) and then we set up the optima dPCR conditions. We validated our assay on 19 samples from a representative panel of human tumors (9 HGNET-BCOR, 5 URCS, 3 HGESS, and 2 PMMTI) in which BCOR-ITD status was known using at least one other method including RNA sequencing, RT-PCR or DNA-methylation profiling for CNS tumors. Our results showed that our technique was 100% sensitive and specific. DPCR detected BCOR-ITD in 13/19 of the cases; in the remaining 6 cases additional RNA-sequencing revealed BCOR gene fusions. To conclude, in the era of histomolecular classification of human tumors, our modified dPCR assay is of particular interest to detect BCOR-ITD since it is a robust and less expensive test that can be applied to a broad spectrum of cancers that share this alteration.

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.

Imaging of bone and soft tissue BCOR-rearranged sarcoma.

With recent advances in molecular research, an ever-increasing number of undifferentiated round cell sarcomas without the characteristic gene fusions of Ewing sarcoma are being discovered. One specific subtype termed BCOR-rearranged sarcoma belongs to this group. Previously termed 'Ewing-like' sarcoma, it was formally included with undifferentiated round cell tumours in the 2013 WHO Classification of Soft Tissue and Bone Tumours. However, in the 2020 WHO Classification, BCOR-sarcoma is now recognized as a distinct entity due to particular morphological and immunohistochemical features and differing clinical outcomes. As with classical Ewing sarcoma, osseous BCOR-rearranged sarcoma is an aggressive tumour with a similar clinical presentation. However, there are only a small handful of case series and isolated reports detailing the imaging characteristics, typically demonstrating an aggressive bone lesion with a large soft tissue mass. Soft tissue BCOR-sarcoma is even rarer. The aim of the current review is to describe the patient demographics, lesion locations and various imaging characteristics of histologically proven cases of musculoskeletal bone and soft tissue BCOR-sarcoma as described in the literature.

A case of undifferentiated small round cell sarcoma associated with the CIC-DUX4 fusion gene

A case of undifferentiated small round cell sarcoma associated with the CIC-DUX4 fusion gene

Detection of Structural Variants in Circulating Cell-Free DNA from Sarcoma Patients Using Next Generation Sequencing.

Simple SummaryAccurate diagnosis of sarcoma can be difficult as there are over 100 different subtypes. Approximately one third of sarcomas are characterised by subtype-specific genetic variants, which are routinely detected by the molecular testing of tumour biopsies. Recent studies have shown the potential use of next generation sequencing (NGS) for variant detection in circulating tumour DNA (ctDNA), which is DNA released from tumour cells into the bloodstream. Our feasibility study is the first to demonstrate the application of a custom NGS gene panel, targeting genetic variants in several sarcoma subtypes using ctDNA samples.Circulating tumour DNA (ctDNA) analysis using next generation sequencing (NGS) is being implemented in clinical practice for treatment stratification and disease monitoring. However, using ctDNA to detect structural variants, a common occurrence in sarcoma, can be challenging. Here, we use a sarcoma-specific targeted NGS panel to identify translocations and copy number variants in a cohort of 12 tissue specimens and matched circulating cell-free DNA (cfDNA) from soft tissue sarcoma patients, including alveolar rhabdomyosarcoma (n = 2), Ewing’s Sarcoma (n = 2), synovial sarcoma (n = 2), extraskeletal myxoid chondrosarcoma (n = 1), clear cell sarcoma (n = 1), undifferentiated round cell sarcoma (n = 1), myxoid liposarcoma (n = 1), alveolar soft part cell sarcoma (n = 1) and dedifferentiated liposarcoma (n = 1). Structural variants were detected in 11/12 (91.6%) and 6/12 (50%) of tissue and plasma samples, respectively. Structural variants were detected in cfDNA at variant allele frequencies >0.2% with an average sequencing depth of 1026×. The results from this cohort show clinical potential for using NGS in ctDNA to aid in the diagnosis and clinical monitoring of sarcomas and warrant additional studies in larger cohorts.

Genomic Analysis of Congenital Myeloid Sarcoma Identifies Significant Bone Marrow Involvement in the Absence of Morphologic Blasts

Myeloid sarcoma is a tumor mass consisting of blasts at extramedullary sites, most frequently the skin and soft tissues. Skin involvement, also termed leukemia cutis, is a well-described entity in congenital leukemia and is present in approximately 50% of patients diagnosed within the first 4 weeks of life. Most cases of congenital leukemia cutis harbor KMT2A rearrangements, as do up to 80% of cases of infantile leukemia, and are typically accompanied by bone marrow involvement. Here we describe a rare CIC-rearrangement as the driver mutation for a case of congenital cutaneous myeloid sarcoma in a newborn female who was noted at birth to have a violaceous, nodular rash. Skin biopsy of the nodular rash shortly after birth with immunohistochemical staining was consistent with myeloid sarcoma. Bilateral bone marrow aspirates and biopsies were also performed, but failed to reveal an aberrant blast population by morphology and flow cytometry. Cytogenetics of the cutaneous myeloid sarcoma was significant for t(10;19)(q23;q13.2) and fluorescence in situ hybridization performed on the tumor confirmed a CIC-rearrangement. CIC-rearranged sarcomas are a new entity of undifferentiated small round cell sarcoma characterized by fusion events involving the CIC gene but are not a known to be driver mutations in myeloid neoplasms. Despite the absence of a blast population in the bone marrow, 75% of analyzed metaphases carried the t(10;19)(q23;q13.2). To further explore the underlying genomic events, whole genome, exome, and transcriptome sequencing was performed on both sarcoma and bone marrow specimens. Sequencing revealed an in-frame CIC-NUTM2A fusion gene present in both the skin and the bone marrow which has been previously described in a single case of undifferentiated soft tissue sarcoma. There were no large-scale chromosomal losses or gains and no copy neutral loss of heterozygosity events. Two exonic single nucleotide variations (SNVs) were detected, both of which were limited to the skin sarcoma and not predicted to be pathogenic. In vitro and in vivo modeling demonstrated that the CIC-NUTM2A fusion protein was highly leukemogenic. Colony forming assays performed using transduced murine bone marrow revealed that the CIC-NUTM2A fusion conferred self-renewal in contrast to CIC, NUTM2A, and the reciprocal NUTM2A-CIC product which failed to serially replate (p&amp;lt;0.001). Transplantation of CIC-NUTM2A modified murine bone marrow cells resulted in a fully penetrant myeloid leukemia with a median survival of 21 days in primary transplants and 16 days in secondary transplants. Transcriptome analysis of these tumors revealed a distinct gene expression profile when compared to several classic myeloid associated fusion genes including AML1-ETO and MLL-AF6. To further understand the acquisition of a malignant phenotype by morphology between the bone marrow and the sarcoma, targeted deep sequencing was performed for all tier 1, 2 and 3 mutations identified by whole genome and exome sequencing. A shared ancestral clone was identified in both specimens along with three subclones specific to the sarcoma. Four SNVs acquired in the sarcoma were found to be present in regulatory regions of genes that were also differentially expressed between the sarcoma and the bone marrow including C6orf120, SMURF1, TJAP1, and PID1. PID1 was found to be downregulated in the malignant sarcoma specimen and has been previously shown to be a regulator of the AKT/PI3K pathway. Low PID1 expression has been associated with poor outcomes in other malignancies, including pediatric glioblastoma. A genome wide CRISPR screen of our CIC-NUTM2A positive murine leukemia cells revealed an enrichment for PID1 deficient cells as well as PTEN confirming the cooperativity between CIC-NUTM2A and the AKT/PI3K pathway (p=0.009 and p=0.005 respectively). In conclusion, we describe a rare fusion gene, CIC-NUTM2A, which leads to an aggressive myeloid malignancy in both humans and mice. Targeted deep sequencing demonstrated the clonal evolution from the bone marrow and acquisition of a cooperating mutation targeting the AKT/PI3K pathway in a subset of extramedullary cells that led to morphologic transformation. A thorough interrogation of the bone marrow in patients with myeloid sarcoma is warranted even in the absence of morphologic and immunophenotypic blasts by flow cytometry to optimally track residual disease during treatment. Disclosures No relevant conflicts of interest to declare.

The 2020 WHO Classification of Soft Tissue Tumours: news and perspectives.

SummaryMesenchymal tumours represent one of the most challenging field of diagnostic pathology and refinement of classification schemes plays a key role in improving the quality of pathologic diagnosis and, as a consequence, of therapeutic options. The recent publication of the new WHO classification of Soft Tissue Tumours and Bone represents a major step toward improved standardization of diagnosis. Importantly, the 2020 WHO classification has been opened to expert clinicians that have further contributed to underline the key value of pathologic diagnosis as a rationale for proper treatment. Several relevant advances have been introduced. In the attempt to improve the prediction of clinical behaviour of solitary fibrous tumour, a risk assessment scheme has been implemented. NTRK-rearranged soft tissue tumours are now listed as an “emerging entity” also in consideration of the recent therapeutic developments in terms of NTRK inhibition. This decision has been source of a passionate debate regarding the definition of “tumour entity” as well as the consequences of a “pathology agnostic” approach to precision oncology. In consideration of their distinct clinicopathologic features, undifferentiated round cell sarcomas are now kept separate from Ewing sarcoma and subclassified, according to the underlying gene rearrangements, into three main subgroups (CIC, BCLR and not ETS fused sarcomas) Importantly, In order to avoid potential confusion, tumour entities such as gastrointestinal stroma tumours are addressed homogenously across the different WHO fascicles. Pathologic diagnosis represents the integration of morphologic, immunohistochemical and molecular characteristics and is a key element of clinical decision making. The WHO classification is as a key instrument to promote multidisciplinarity, stimulating pathologists, geneticists and clinicians to join efforts aimed to translate novel pathologic findings into more effective treatments.

Preliminary Results of a Phase Ib Study of Olaparib with Concomitant Radiotherapy in Locally Advanced/Unresectable Soft-Tissue Sarcoma from the French Sarcoma Group

The poly(ADP-ribose) polymerase (PARP) inhibitor olaparib (O) has radiosensitizing properties in several tumor models including sarcomas. We studied pharmacokinetics (PK), safety and toxicity of O with external beam radiation therapy (EBRT) in patients with soft-tissue sarcomas (STS). Patients with locally advanced STS (with or without distant metastases) were eligible for the study. In this phase I study based on a time-to-event continual reassessment method (TITE-CRM) design, patients were treated with escalating doses of O administered in combination with EBRT (59.4 Gy in 33 fractions of 1.8 Gy). Four dose levels of O were explored: DL1:25 mg, DL2:50 mg, DL3:100 mg, DL4:150 mg BID. Tumor response was assessed by investigators according to RECIST 1.1. 26 pts were enrolled (10 males, 16 females). Eleven patients had undifferentiated pleomorphic sarcoma, six patients had liposarcoma, 2 myxofibrosarcoma, 2 synovial sarcoma, 1 myxo-inflammatory fibroblastic sarcoma, 1 MPNST, 1 leiomyosarcoma, 1 phyllode sarcoma, 1 undifferentiated round-cell sarcoma. There were 1 DLT on at DL 1 (n = 5), 1 DLT at DL2 (n = 7), 0 DLT at DL3 (n = 11) and 1 DLT at DL4 (n = 3). RP2D was 100 mg BID. Most common adverse events related to O and/or EBRT were acute dermatitis (100%, G3/4 50%), fatigue (42%, G3/4 0%), nausea (38.5%, G3/4 0%), anorexia (19.2%, G3/4 0%) and anemia (15.3%, G3/4 0%). Surgery of the primary tumor was done in 7 patients; 3 of them presented grade 5 post-operative toxicity. Of 20 evaluable patients, 10 had tumor shrinkage resulting in partial response in 3 patients (one liposarcoma, one phyllode sarcoma and one undifferentiated pleomorphic sarcoma). 13 patients had stable disease, 3 patients had progressive disease and 1 NE. The median PFS and OS were 17.9 and 15.9 months, respectively. This study shows that the combination of O with EBRT is well tolerated and lead to encouraging downstaging and survival rates in patients with locally advanced STS. Currently we are enrolling 15 additional pts at the recommended dose of O to further evaluate efficacy and safety.

Clinicopathologic and molecular features of undifferentiated round cell sarcomas of bone and soft tissues, including BCOR-CCNB3 and CIC-DUX4 test results

Clinicopathologic and molecular features of undifferentiated round cell sarcomas of bone and soft tissues, including BCOR-CCNB3 and CIC-DUX4 test results

Small Round Blue Cell Sarcoma Other Than Ewing Sarcoma: What Should an Oncologist Know?

The diagnosis of round cell sarcomas has changed rapidly over the last decade, causing much diagnostic confusion for pathologists and oncologists. The advances in diagnosis are largely due to the advent of next-generation sequencing techniques, which allowed the recognition of novel gene fusions in round cell sarcomas. The new 5th edition of the WHO Classification of Tumors of Soft Tissue and Bone recognizes four subgroups of undifferentiated round cell sarcomas: Ewing sarcoma, CIC-rearranged sarcomas, BCOR-altered sarcomas, and sarcomas with EWSR1-non-ETS fusions, in addition to desmoplastic small round cell tumor. This classification is based on a variety of publications showing that each of these molecular subtypes has unique clinical and prognostic characteristics distinct from Ewing sarcoma, therefore supporting the validity of recognizing these as discrete diagnostic entities. Despite our improved ability to diagnose these new round cell sarcomas, there remains confusion on how best to identify and treat these tumors. However, several key clinicopathologic features can point the physician toward the correct diagnosis. The goal of the following article is to emphasize the key clinical, pathologic, molecular, and prognostic differences between Ewing sarcoma and these non-Ewing round cell malignancies to improve recognition of these rare diseases.

Imaging features and clinical course of undifferentiated round cell sarcomas with CIC-DUX4 and BCOR-CCNB3 translocations.

To describe the pre-treatment imaging features and clinical course of undifferentiated round cell sarcomas with CIC-DUX4 and BCOR-CCNB3 translocations. In this retrospective study, several pre-treatment imaging features (tumor location, size, enhancement pattern, necrosis, flow voids, calcification, and FDG avidity) and the clinical course of patients were evaluated. In 12 patients with CIC-DUX4 sarcomas (median age, 24 years; range, 12-75), sarcomas were located in the soft tissue (n = 10), bone (n = 1), and lungs (n = 1). On MRI, all 10 CIC-DUX4 sarcomas presented as a large necrotic mass (mean size 6.7 cm, range 2.3-11.3) with 100% demonstrating contrast enhancement, 60% showing flow voids, and 20% demonstrating fluid-fluid levels. On PET, the mean SUVmax was 13.2 (range, 8.5-18.1). Among 12 patients with follow-up, 3 died within a year of diagnosis. The most common site of metastases was the lungs (5/12). In 5 patients with BCOR-CCNB3 sarcomas (median age, 14 years; range, 2-17), sarcomas were located in the spine (n = 2), femur (n = 1), tibia (n = 1), and pelvis (n = 1). On radiograph or CT, 2 were lytic, 3 were sclerotic. Soft tissue calcifications occurred in 40% of BCOR-CCNB3 sarcomas. On MRI, all 3 BCOR-CCNB3 tumors enhanced with 33% demonstrating flow voids and 66% exhibiting necrosis. On PET, the mean SUVmax was 6.3 (range 5.7-6.9). CIC-DUX4 sarcomas often present as necrotic and hypermetabolic soft tissue masses while sarcomas with BCOR-CCNB3 translocations are vascular bone lesions with necrosis at imaging. CIC-DUX4 sarcomas are clinically more aggressive than BCOR-CCNB3 sarcomas.

The 2020 WHO Classification

The fifth edition of the World Health Organization Classification of Tumors of Soft Tissue and Bone was published in early 2020. The revisions reflect a consensus among an international expert editorial board composed of soft tissue and bone pathologists, geneticists, a medical oncologist, surgeon, and radiologist. The changes in the soft tissue tumor chapter notably include diverse, recently described tumor types (eg, atypical spindle cell/pleomorphic lipomatous tumor, angiofibroma of soft tissue, and CIC-rearranged sarcoma), new clinically significant prognostic information for a variety of existing entities (eg, dedifferentiated liposarcoma and solitary fibrous tumor), and a plethora of novel genetic alterations, some of practical diagnostic relevance (eg, NAB2-STAT6 in solitary fibrous tumor, FOSB rearrangements in epithelioid hemangioma and pseudomyogenic hemangioendothelioma, and SUZ12 or EED mutations in malignant peripheral nerve sheath tumor, leading to loss of H3K27 trimethylation). In this review, we highlight the major changes to the soft tissue chapter in the 2020 World Health Organization Classification, as well as the new chapter on undifferentiated small round cell sarcomas, with a focus on updates in diagnostic categories, prognostication, and novel markers. Recent discoveries in molecular genetics are also discussed, particularly those of immediate utility in differential diagnosis, including protein correlates detectable using immunohistochemistry.