EWSR1-The Most Common Rearranged Gene in Soft Tissue Lesions, Which Also Occurs in Different Bone Lesions: An Updated Review

Metastatic Testicular Sex Cord Tumor Harboring a EWSR1::ATF1 Gene Fusion-A Case Report of a Novel Neoplasm: "Inflammatory and Nested Testicular Sex Cord Tumor"

We present a case report of a 54-year-old male with a metastatic testicular sex cord tumor harboring a EWSR1::ATF1 gene fusion. The tumor displayed a solid and nested architecture with sclerotic stroma and variable inflammatory infiltrate, and was positive for SF-1, inhibin, EMA, CD30, and WT1 expression. Further genetic analysis identified a EWSR1::ATF1 gene fusion. Overall findings were consistent with an "inflammatory and nested testicular sex cord tumor," a recently described testicular neoplasm characterized by EWSR1::ATF1 gene fusion and aggressive clinical behavior. Due to the aggressive nature of this entity and the limited response to current treatment options available, identification of potential biomarkers for early diagnosis and targeted therapies are critical. This case report provides important insights into the genomic landscape of testicular sex cord-stromal tumors, especially within the CTNNB1-negative subset of patients with an aggressive clinical course, and further supports the distinction of "inflammatory and nested testicular sex cord tumor" as a separate entity from Sertoli cell tumors due to its characteristic morphological, immunohistochemical and molecular, features and clinical behavior.

Hepatocellular Carcinoma LINC01116 Outcompetes T Cells for Linoleic Acid and Accelerates Tumor Progression

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer with a highly immunosuppressive tumor microenvironment and a typical pattern of disturbances in hepatic lipid metabolism. Long non-coding RNAs are shown to play an important role in the regulation of gene expression, but much remains unknown between tumor microenvironment and lipid metabolism as a bridging molecule. Here, long intergenic nonprotein coding RNA 01116 (LINC01116) acts as this molecular which is frequently upregulated in HCC patients and associated with HCC progression in vitro and in vivo is identified. Mechanistically, LINC01116 stabilizes EWS RNA-binding protein 1 (EWSR1) by preventing RAD18 E3 Ubiquitin Protein Ligase (RAD18) -mediated ubiquitination. The enhanced EWSR1 protein upregulates peroxisome proliferator activated receptor alpha (PPARA) and fatty acid binding protein1 (FABP1) expression, a long-chain fatty acid (LCFA) transporter, and thus cancer cells outcompete T cells for LCFAs, especially linoleic acid, for seeding their own growth, leading to T cell malfunction and HCC malignant progression. In a preclinical animal model, the blockade of LINC01116 leads to enhanced efficacy of anti-PD1 treatment accompanied by increased cytotoxic T cell and decreased exhausted T cell infiltration. Collectively, LINC01116 is an immunometabolic lncRNA and the LINC01116-EWSR1-PPARA-FABP1 axis may be targetable for cancer immunotherapy.

Back to the future! Selected bone and soft tissue neoplasms with shared genetic alterations but differing morphological and immunohistochemical phenotypes

Bone and soft tissue tumors (BST) are a highly heterogeneous group largely classified by their line of differentiation, based on their resemblance to their normal counterpart in adult tissue. Yet, rendering a specific diagnosis can be challenging, primarily due to their rarity and overlapping histopathologic features or clinical presentations. Over the past few decades, seemingly histogenetic-specific gene fusions/translocations and amplifications have been discovered, aiding in a more nuanced classification, leading to well-established objective diagnostic criteria and the development of specific surrogate ancillary tests targeting these genetic aberrations (e.g., immunohistochemistry). Ironically, the same research also has revealed that some specific tumor subtypes may be the result of differing and often multiple gene fusions/translocations, but, more interestingly, identical gene fusions may be present in more than one phenotypically and biologically distinct neoplasm, sometimes with entirely different clinical behavior. Prime examples include, EWSR1::ATF1 and, less commonly, EWSR1::CREB1 gene fusions present in both clear cell sarcoma, a malignant high-grade tumor with melanocytic differentiation, and angiomatoid fibrous histiocytoma, a mesenchymal neoplasm of intermediate malignancy with a generally indolent course. Similarly, MDM2 amplification, once deemed to be pathognomonic for atypical lipomatous tumor/well differentiated and dedifferentiated liposarcoma, has been documented in a range of additional distinct tumors, including low grade osteosarcomas (e.g. low grade central and surface parosteal) and high-grade intimal sarcomas, amongst others. Such findings reinforce the importance of careful attention to morphological and clinicoradiological features and correlation with molecular testing before rendering a specific diagnosis. Future classification systems in BST neoplasms cannot be solely based on molecular events and ideally will balance morphologic features with molecular analysis. Herein, we provide a narrative literature review of the more common BST neoplasms with shared genetic events but differing demographics, morphology, immunophenotype, and clinical behavior, re-emphasizing the importance of the hematoxylin and eosin slide and the "eye" of the practicing pathologist.

A Rare Case of a Malignant Epithelioid Neoplasm With an Underlying Novel EWSR1::ZBT44 Fusion, Identified on Next-Generation Sequencing (NGS)

The clinicopathological spectrum of undifferentiated round cell sarcomas of bone and soft tissues is expanding after the 5th edition of the WHO classification. A 23-year-old male patient presented with a lump in his left thigh of 3 months' duration. Radiological examination revealed a well-defined, solid-cystic lobulated, soft tissue lesion in the proximal medial region of his left thigh, measuring 7.7 cm in the largest dimension. The referring diagnosis was an epithelioid sarcoma. Histopathological review of the tumor sections revealed a cellular tumor composed of malignant epithelioid to focally "rhabdoid-like" cells in a variable hyalinized and myxoid stroma with geographic areas of necrosis. In addition, there were areas reminiscent of hemangiopericytomatous vasculature. By immunohistochemistry, the tumor cells were diffusely positive for CD34, focally and distinctly for pan keratin (AE1/AE3). INI1/SMARCB1 and SMARCA4 (BRG1) were diffusely positive (normal). Next-generation sequencing with a wide sarcoma panel revealed EWSR1exon8::ZBT44exon4 fusion. The present example constitutes the first malignant epithelioid tumor with a hemangiopericytomatous growth pattern, exhibiting this rare fusion. The differential diagnoses of this tumor and their corresponding immunohistochemical profile are discussed. This example highlights the value of NGS in unraveling rare fusions and in differentiating these tumors from their several mimics.

An unusual cystic presentation of pelvic skeletal Ewing sarcoma: a case series

Ewing sarcoma (ES) is the second most common primary malignant bone tumour in children and adolescents. About 14.5% of primary malignancies develop in pelvic bones, where they typically have worse prognoses than extremity or acral sarcomas. It usually presents with aggressive features on radiology scans, but may also present with different radiological characteristics. In this series, we describe rare appearances of pelvic skeletal Ewing sarcoma, with large extraosseous cystic component on imaging, defined by the presence of fluid-filled spaces in the extraosseous tumour lesion, which distinguishes it from the solid nature of conventional ES. We report 3 cases of cystic presentation of ES, with imaging features supporting diagnosis of a primary malignant bone tumour arising from the superior pubic ramus with associated massive intrapelvic solid and cystic mass. CT-guided biopsy provided diagnosis of ES, with large intrapelvic soft tissue and cystic component. These patients underwent neo-adjuvant chemotherapy and proton beam therapy with significant reduction in size of the solid components, while the cystic components remained relatively unchanged. Two patients underwent surgical resection of the tumour (navigated P3 internal hemipelvectomy and hemipelvis P2/P3 resection, respectively), and one patient died while on treatment. In both who underwent surgery, histology showed ES with margins clear and more than 99% of treatment-induced necrosis. To the authors' knowledge, this unusual presentation of pelvic ES is described for the first time in the literature as a case series, with particular reference to atypical extraosseous cystic changes, along with the clinical and radiological characteristics, and their treatment.

Small cell osteosarcoma versus fusion-driven round cell sarcomas of bone: retrospective clinical, radiological, pathological, and (epi)genetic comparison with clinical implications

Small cell osteosarcoma (SCOS), a variant of conventional high-grade osteosarcoma (COS), may mimic fusion-driven round cell sarcomas (FDRCS) by overlapping clinico-radiological and histomorphological/immunohistochemical characteristics, hampering accurate diagnosis and consequently proper therapy. We retrospectively analyzed decalcified formalin-fixed paraffin-embedded (FFPE) samples of 18 bone tumors primarily diagnosed as SCOS by methylation profiling, fusion gene analysis, and immunohistochemistry.In eight cases, the diagnosis of SCOS was maintained, and in 10 cases it was changed into FDRCS, including three Ewing sarcomas (EWSR1::FLI1 in two cases and no identified fusion gene in the third case), two sarcomas with BCOR alterations (KMT2D::BCOR, CCNB3::BCOR, respectively), three mesenchymal chondrosarcomas (HEY1::NCOA2 in two cases and one case with insufficient RNA quality), and two sclerosing epithelioid fibrosarcomas (FUS::CREBL3 and EWSR1 rearrangement, respectively).Histologically, SCOS usually possessed more pleomorphic cells in contrast to the FDRCS showing mainly monomorphic cellular features. However, osteoid was seen in the latter tumors as well, often associated with slight pleomorphism. Also, the immunohistochemical profile (CD99, SATB2, and BCOR) overlapped.Clinically and radiologically, similarities between SCOS and FDRCS were observed, with by imaging only minimal presence or lack of (mineralized) osteoid in most of the SCOSs.In conclusion, discrimination of SCOS, epigenetically related to COS, versus FDRCS of bone can be challenging but is important due to different biology and therefore therapeutic strategies. Methylation profiling is a reliable and robust diagnostic test especially on decalcified FFPE material. Subsequent fusion gene analysis and/or use of specific immunohistochemical surrogate markers can be used to substantiate the diagnosis.

Identification of Novel/Rare EWSR1 Fusion Partners in Undifferentiated Mesenchymal Neoplasms

Recurrent gene fusions (GFs) in translocated sarcomas are recognized as major oncogenic drivers of the disease, as well as diagnostic markers whose identification is necessary for differential diagnosis. EWSR1 is a 'promiscuous' gene that can fuse with many different partner genes, defining different entities among a broad range of mesenchymal neoplasms. Molecular testing of EWSR1 translocation traditionally relies on FISH assays with break-apart probes, which are unable to identify the fusion partner. Therefore, other ancillary molecular diagnostic modalities are being increasingly adopted for accurate classification of these neoplasms. Herein, we report three cases with rare GFs involving EWSR1 in undifferentiated mesenchymal neoplasms with uncertain differential diagnoses, using targeted RNA-seq and confirming with RT-PCR and Sanger sequencing. Two GFs involved hormone nuclear receptors as 3' partners, NR4A2 and RORB, which have not been previously reported. NR4A2 may functionally replace NR4A3, the usual 3' partner in extraskeletal myxoid chondrosarcoma. The third GF, EWSR1::BEND2, has previously been reported in a subtype of astroblastoma and other rare entities, including a single case of a soft-tissue tumor that we discuss in this work. In conclusion, our findings indicate that the catalogue of mesenchymal neoplasm-bearing EWSR1 fusions continues to grow, underscoring the value of using molecular ancillary techniques with higher diagnostic abilities in the routine clinical setting.

Activity of pazopanib in EWSR1-NFATC2 translocation-associated bone sarcoma

Pazopanib is a multi-kinase inhibitor that is currently approved for treatment of advanced renal cell carcinoma and chemotherapy-refractory soft tissue sarcoma. In this case report, we discuss the case of a patient with a EWSR1-NFATC2 fusion positive bone sarcoma who had exceptional tumor control through using pazopanib and surgery for an overall duration exceeding 5 years. We also review the literature on EWSR1-NFATC2 translocation-associated sarcomas and use of pazopanib in bone sarcomas.

Investigation of Diagnostic and Prognostic Value of CLEC4M of Non-Small Cell Lung Carcinoma Associated with Immune Microenvironment

Purpose

C-type lectin domain family 4 member M (CLEC4M) has been found to be involved in the occurrence and development of cancer, but its role in NSCLC remains to be fully explored. Our work aims to evaluate the diagnostic and prognostic value of CLEC4M in NSCLC and to investigate the underlying mechanisms of CLEC4M in the immune microenvironment of NSCLC.

Methods

Integrating publicly accessible data and clinical tissue samples to verify the expression of CLEC4M in NSCLC. The diagnostic value of CLEC4M was determined by receiver operating characteristic (ROC) curve. Kaplan-Meier survival analysis, nomogram plot, univariate and multivariate Cox regression models were performed to evaluate the prognostic impact of CLEC4M on NSCLC patients. The correlation between CLEC4M and tumor immune infiltration was estimated using TIMER and UALCAN databases. Functional assessments including GO, KEGG pathway and GSEA analyses were implemented to illustrate the potential mechanisms of CLEC4M in NSCLC.

Results

CLEC4M was significantly downregulated in NSCLC tissue, as confirmed by immunohistochemistry of clinical tissues. The high AUC value of ROC curves demonstrated the diagnostic accuracy of CLEC4M in NSCLC. Additionally, low CLEC4M expression was associated with poor survival in NSCLC patients. Furthermore, CLEC4M was found to be significantly associated with tumor immune infiltration, and CLEC4M may be involved in immune activation and proliferation inhibition through the functional assessment, suggesting that CLEC4M may be a therapeutic target for NSCLC patients.

Conclusion

Our findings reveal CLEC4M is significantly downregulated in NSCLC tissues, and illustrate the diagnostic and prognostic value of CLEC4M in NSCLC, as well as its potential serve as an immune-related therapeutic target.

A Low Grade Nasopharyngeal sarcoma With FUS::NACC1 Fusion and Immunohistochemical Evidence of Epithelial Differentiation: Expanding the Clinicopathologic Spectrum of an Emerging Entity

BACKGROUND

RNA sequencing of unclassified soft tissue tumors has allowed for definition of multiple new entities. Antonescu et al. recently reported three case of low grade sarcoma with recurrent EWSR1/FUS::NACC1 fusion and distinctive storiform architecture that were suggestive of a novel tumor type.

METHODS

Here, we present a case of an additional sarcoma with FUS::NACC1 fusion that arose in the head and neck and showed immunohistochemical evidence of epithelial differentiation.

RESULTS

A 41 year old woman presented with throat and inner ear pain and was found to have a nasopharyngeal mass. Biopsy highlighted a spindle cell neoplasm composed of bland cells arranged in a tight storiform pattern. On immunohistochemistry, the tumor cells were focally positive for S100 in a fibrillary pattern but were also positive for high molecular weight cytokeratin, p40, and CD34. RNA sequencing demonstrated a FUS::NACC1 fusion. The patient remains free of disease 2 years after surgical resection.

CONCLUSION

These findings confirm the previously-reported recurrent storiform histology in sarcomas with EWSR1/FUS::NACC1 fusion while simultaneously expanding the immunohistochemical spectrum of this entity to include overt epithelial differentiation. With involvement of a head and neck mucosal site, these findings also expand the differential diagnosis to include multiple mesenchymal entities including spindle cell squamous cell carcinoma. Further recognition of this emerging entity via expanded RNA sequencing panels will be necessary to determine the prevalence of these unique features.

Metastatic sporadic paraganglioma with EWSR1::CREM gene fusion: A unique molecular profile that expands the phenotypic diversity of the molecular landscape of the EWSR1::CREM gene fusion positive tumors

Chromosomal translocations with gene fusions are uniquely rare events in paraganglioma, mostly involving UBTF::MAML3 gene fusion. Precedent literature suggests that tumors involving MAML3 gene fusion correlate with poor clinical outcomes. Herein, we report a case of metastatic sporadic paraganglioma harboring EWSR1::CREM gene fusion in a 36-year-old male, that has not been previously described. The patient presented with large paraspinal mass that was resected the same year. Tumor recurred 3-years later and on further work-up, patient was found to have metastases involving both lungs. Histopathologic evaluation of the original primary tumor showed tightly packed irregular nests and cords of cells containing palely eosinophilic cytoplasm. Features considered atypical included: areas of solid growth pattern, coagulative tumor necrosis, focal cellular atypia and angiolymphatic invasion were also identified. By immunohistochemistry, the tumor cells were positive for synaptophysin and chromogranin and negative for keratin. The S100 stain highlights the sustentacular cells and the Ki-67 proliferation index of 15%. The recurrence specimen was similar but showed increased cellularity, atypia, necrosis, and proliferative activity (Ki-67 proliferation index of 35%). CT guided biopsy of the right lung lesion was consistent with metastasis. Next generation sequencing identified EWSR1::CREM fusion. The breakpoints were found in chromosome 22: 29683123 for EWSR1 exon 7 (NM_005243.3) and at chromosome 10:35495823 for CREM exon 6 (NM_001267562.1). Fluorescence in situ hybridization for EWSR1 gene rearrangement was positive. In summary, we report a case of metastatic paraganglioma with EWSR1::CREM gene fusion, not previously described in this entity, and expands on the phenotypic diversity within the genetic landscape of EWSR1::CREM gene fusion positive tumors.

EWSR1::SMAD3-rearranged fibroblastic tumor: A case with twice recurrence and literature review

EWSR1::SMAD3-rearranged fibroblastic tumor is a recently described entity that mostly occurs in acral locations. Only 15 cases have been reported in the English literature, with a wide age range and marked female predominance. The most common sites are the foot, followed by the hand and the distal lower leg. There are four cases that recurred locally during 5-120 months of follow-up, with no metastases to date. Herein, we presented a case of EWSR1::SMAD3-rearranged fibroblastic tumor that recurred twice in a 20-year-old man. The patient presented with a second recurrent painful nodule in the left plantar of the second toe. Grossly, the lesion was pale solid and well-defined, measuring 9 × 8 × 9 mm in size. Histological examination revealed a monomorphic spindle cell tumor composed of cellular fascicles of bland fibroblasts in a collagenous to myxoid stroma with low mitotic activity, which evoked a wide spectrum of differential diagnoses. Immunohistochemically, the tumor cells were diffusely and strongly positive for ERG while negative for S100, α-SMA, CD34, and other vascular markers. An unbalanced rearrangement of EWSR1 was demonstrated by fluorescence in situ hybridization (FISH), and a gene fusion between EWSR1 exon 7 and SMAD3 exon 6 was confirmed by RT-PCR and Sanger sequencing. This case recurred twice within 6 years with no sign of further relapse and metastasis at another 9-month follow-up since the last surgery, indicating that this tumor was benign but prone to local recurrence. Nevertheless, more cases and further studies are needed to better interpret the biological behavior of this new entity.

EWSR1::YY1 fusion positive peritoneal epithelioid mesothelioma harbors mesothelioma epigenetic signature: Report of 3 cases in support of an emerging entity

Mesothelioma is a rare, aggressive malignant neoplasm of mesothelial origin. A small subset of peritoneal mesothelioma is driven by recurrent gene fusions, mostly EWSR1/FUS::ATF1 fusions, with predilection for young adults. To date, only two cases of mesothelioma harboring EWSR1::YY1 fusions have been described. We present three additional cases of EWSR1::YY1-fused peritoneal mesotheliomas, two localized and one diffuse, all occurring in the peritoneum of middle-aged adults (2 females and 1 male), and discovered incidentally by imaging or during surgery performed for unrelated reasons. None presented with symptoms or had a known history of asbestos exposure. All three cases were cellular epithelioid neoplasms with heterogeneous architectural patterns comprising mostly solid nests and sheets with variably papillary and trabecular areas against collagenous stroma. Cytologically, the cells were monomorphic, polygonal, epithelioid cells with dense eosinophilic cytoplasm and centrally located nuclei. Overt mitotic activity or tumor necrosis was absent. All cases showed strong diffuse immunoreactivity for pancytokeratin, CK7, and nuclear WT1, patchy to negative calretinin, retained BAP1 expression, and were negative for Ber-EP4 and MOC31. RNA-sequencing confirmed in-frame gene fusion transcripts involving EWSR1 exon 7/8 and YY1 exon 2/3. By unsupervised clustering analysis, the methylation profiles of EWSR1::YY1-fused mesotheliomas clustered similarly with EWSR1/FUS::ATF1-fused mesotheliomas and conventional mesotheliomas, suggesting a mesothelioma epigenetic signature. All three patients underwent surgical resection or cytoreductive surgery of the masses. On follow-up imaging, no recurrence or progression of disease was identified. Our findings suggest that EWSR1::YY1-fusion defines a small subset of peritoneal epithelioid mesothelioma in middle-aged adults without history of asbestos exposure.

Identification of EWSR1 rearrangements in patients with immature hematopoietic neoplasms: A case series and review of literature

Rearrangement of the EWSR1 gene (22q12.2) is a well-recognized genetic lesion in bone and soft tissue tumors. However, few reports have suggested that EWSR1 rearrangements may also occur in the setting of hematopoietic tumors. We herein describe two cases of immature hematopoietic neoplasms presenting with EWSR1 rearrangements. The first occurred in a 41-year-old female diagnosed with mixed-phenotype acute leukemia, B/T/myeloid, in which conventional chromosome analysis revealed a t(2;22)(q35;q12). Further analysis with whole genome sequencing revealed that this rearrangement led to an EWSR1::FEV gene fusion. The second case was identified in an 18-year-old male with a high-grade B-cell lineage malignant neoplasm with immature features in which conventional chromosome analysis revealed a t(17;22)(q25;q12). Mate-pair sequencing, a next generation sequencing-based assay, was performed and revealed three in-frame chimeric gene fusions involving the EWSR1, TEF and STRADA gene regions. This report further expands the repertoire of hematopoietic neoplasms with EWSR1 fusions and partner genes involved in these rearrangements.

A novel EWSR1-HOXB13 rearrangement in a fibroblastic tumor from the abdomen of a young woman

We describe a novel EWSR1-HOXB13-fusion in a fibroblastic tumor from the abdominal wall of a 29-year-old woman. This tumor caused intermittent intense pain and had grown to approximately 5 cm in size over two years. The tumor was located beneath subfascial section of the abdominal wall and was invading the abdominal cavity and pressing on the liver. The tumor was well-circumscribed and consisted of intersected fascicles of monomorphic spindle-shaped cells with uniform ovoid nuclei lacking nuclear pleomorphism or mitotic activity. This tumor was immunohistochemically negative for pan-cytokeratin AE1/AE3, desmin, SMA, S100, myogenin, MyoD1, CD34, melanosome, SOX10, STAT6, SS18-SSX, and ERG. H3K27me3 was retained. RNA sequencing revealed a unique EWSR1-HOXB13-fusion, and strong, diffuse nuclear immunostaining for HOXB13 was observed. No local recurrence or evident distant metastasis were observed over eight months without chemotherapy, implying that the behavior of this tumor is not yet known.