Mesenchymal Tumors with EWSR1 Gene Rearrangements

Primary pulmonary myxoid sarcoma: A case report

Pulmonary myxoid sarcoma is an rare and poorly understood malignant neoplasm that primarily arises within the pulmonary tissue. Characterized by its distinctive histological features of myxoid stroma and spindle-shaped cells, this neoplasm poses significant diagnostic and therapeutic challenges due to its rarity and the non-specific nature of its clinical presentation. Current knowledge regarding the pathogenesis, optimal therapeutic strategies and prognostic factors for pulmonary myxoid sarcoma remains limited, primarily due to the scarcity of reported cases and comprehensive studies. The present study reports a case of pulmonary myxoid sarcoma. A 41-year-old male was admitted to the Jeonbuk National University Hospital due to a pulmonary mass in the left lower lobe discovered during a routine health check-up. A CT scan performed at our hospital revealed a nodule ~1 cm in size in the mediobasal segment of the left lower lobe, with relatively well-defined margins and significant enhancement. A wedge resection was performed for diagnosis and treatment, and frozen section examination showed a high likelihood of pleomorphic adenoma. The histological findings of the permanent section examination revealed an abundant myxoid matrix with embedded spindle, stellate and rounded/epithelioid cells arranged in a reticular pattern. The tumor cells exhibited mild to moderate cellular atypia, with rare mitotic figures. Immunohistochemistry showed positive staining for vimentin and negative findings for myoepithelial cell markers such as calponin, high-molecular weight cytokeratin and p63. The presence of the EWSR1-CREB1 fusion was confirmed through fluorescence in situ hybridization and reverse transcription-PCR analyses. Based on these findings, the nodule was diagnosed as pulmonary myxoid sarcoma.

"Putting the cart before the horse": an update on promiscuous gene fusions in soft tissue tumors

The ever-increasing availability and affordability of molecular genetic testing has revolutionized our understanding of the pathogenesis and proper classification of soft tissue tumors but has also brought new challenges. As is known, many soft tissue tumors harbor gene fusion events, and while it was initially thought that individual entities would be defined by single, specific fusions, it quickly became clear that some entities could be caused by several different fusion events (e.g., EWSR1::FLI1, EWSR1::ERG, EWSR1:FEV and others in Ewing sarcoma). More recently, it has become apparent that these fusion events themselves are "promiscuous", appearing in more than one discrete entity (e.g., EWSR1::CREB1 in clear cell sarcoma, angiomatoid fibrous histiocytoma and others). This review article will briefly discuss the best known examples of genetic promiscuity, the EWSR1/FUS::ATF1/CREB1 and ETV6::NTRK3 fusions, and more comprehensively cover recently discovered and less well-known examples of genetic promiscuity, including EWSR1::WT1, MALAT1::GLI1, YAP1::TFE3 and fusions involving members of the FET and ETS gene families.

Superficial Neurocristic FET::ETS Fusion Tumor: Expanding the Clinicopathological and Molecular Genetic Spectrum of a Recently Described Entity

Superficial neurocristic EWSR1::FLI1 fusion tumor is a very recently described, clinically indolent tumor of the skin and superficial soft tissues, which differs in essentially all ways from Ewing sarcoma, despite harboring an identical fusion event. The EWSR1 and FLI1 genes are members of the FET and ETS gene family, respectively, and very rare examples of Ewing sarcoma harbor alternative FET::ETS fusion events, such as EWSR1::ERG, FUS::FLI1, FUS::ERG, EWSR1::ETV4, and others. We report 5 new cases of this very rare entity, harboring in 3 cases alternative FET::ETS fusion events. The tumors occurred in 2 males and 3 females (median age, 14 years, range, 8-69 years) and presented as solitary dermal/subcutaneous masses of the thigh, foot, shoulder, arm, and back (median size, 1.8 cm; range, 1-2 cm). All patients underwent wide excisions; one received adjuvant chemotherapy. Clinical follow-up on 3 patients (median, 24 months; range, 18-31 months) showed all to be without disease. Morphologically, all tumors displayed typical features of this entity as described, with nests of cytologically bland, diffusely S100 protein/SOX10-positive round cells without mitotic activity, surrounded by fibrous bands containing spindled cells with similar nuclear features. The tumors also showed membranous CD99 (4/5) and nuclear NKX2.2 (3/3) expression. RNA sequencing (5 cases) demonstrated FUS::FLI1, FUS::ERG, EWSR1::FLI1, EWSR1::ERG, and a novel FUS::ETV5. Methylation profiling (4 cases) showed all to cluster with previously reported superficial neurocristic EWSR1::FLI1 fusion tumors and apart from conventional and "adamantinoma-like" Ewing sarcoma. Our findings confirm the distinctive clinicopathological features of this very rare, recently described entity and expand its molecular genetic spectrum. Reflecting on these findings, we propose modifying the name of this entity to "superficial neurocristic FET::ETS fusion tumor."

EWSR1::ATF1 fusions characterize a group of extra-abdominal epithelioid and round cell mesenchymal neoplasms, phenotypically overlapping with sclerosing epithelioid fibrosarcomas, and intra-abdominal FET::CREB fusion neoplasms

With the increasing use of next generation sequencing in soft tissue pathology, particularly in neoplasms not fitting any World Health Organization (WHO) category, the spectrum of EWSR1 fusion-associated soft tissue neoplasms has been expanding significantly. Although recurrent EWSR1::ATF1 fusions were initially limited to a triad of mesenchymal neoplasms including clear cell sarcoma of soft tissue, angiomatoid fibrous histiocytoma and malignant gastrointestinal neuroectodermal tumor (MGNET), this family has been expanding. We herein describe 4 unclassified extra-abdominal soft tissue (n = 3) and bone (n = 1) neoplasms displaying epithelioid and round cell morphology and carrying an EWSR1::ATF1 fusion. Affected were 3 males and 1 female aged 20-56 years. All primary tumors were extra-abdominal and deep-seated (chest wall, mediastinum, deltoid, and parapharyngeal soft tissue). Their size ranged 4.4-7.5 cm (median, 6.2). One patient presented with constitutional symptoms. Surgery with (2) or without (1) neo/adjuvant therapy was the treatment. At last follow-up (8-21 months), 2 patients developed progressive disease (1 recurrence; 1 distant metastasis). The immunophenotype of these tumors is potentially misleading with variable expression of EMA (2 of 3), pankeratin (2 of 4), synaptophysin (2 of 3), MUC4 (1 of 3), and ALK (1 of 3). All tumors were negative for S100 and SOX10. These observations point to the existence of heretofore under-recognized group of epithelioid and round cell neoplasms of soft tissue and bone, driven by EWSR1::ATF1 fusions, but distinct from established EWSR1::ATF1-associated soft tissue entities. Their overall morphology and immunophenotype recapitulate that of the emerging EWSR1/FUS::CREB fusion associated intra-abdominal epithelioid/round cell neoplasms. Our cases point to a potentially aggressive clinical behavior. Recognizing this tumor type is mandatory to delineate any inherent biological and/or therapeutic distinctness from other, better-known sarcomas in the differential diagnosis including sclerosing epithelioid fibrosarcoma.

Spinal Cord Astroblastoma With EWSR1-BEND2 Fusion in Female Patients : A Report of Four Cases From China and a Comprehensive Literature Review

Astroblastoma is an extremely rare central nervous system tumor characterized by astroblastic pseudorosettes and vascular hyalinization. Despite these histologic hallmarks, its morphology can vary, occasionally resembling other central nervous system tumors such as ependymoma. A novel tumor entity, astroblastoma, meningioma 1 ( MN1 )-altered, has been identified, featuring MN1 gene rearrangements typically involving BEN-domain containing 2 ( BEND2 ) as a fusion partner. Most astroblastomas arise in the cerebral hemisphere. Here, we report 4 cases of spinal cord astroblastoma in female patients, all showing Ewing sarcoma RNA-binding protein 1 fusion with BEND2 , rather than MN1 . These tumors displayed growth patterns akin to traditional intracranial astroblastomas, with three cases demonstrating high-grade histology, including elevated mitotic activity and necrosis. Interestingly, some cases exhibited positive staining for pan-cytokeratin and hormone receptors. DNA methylation profiling clustered three of the four cases with the reference "AB_EWSR," whereas one case exhibited an independent methylation signature near the reference methylation group "AB_EWSR" and "pleomorphic xanthoastrocytoma." Together with the existing literature, we summarized a total of eleven cases, which predominantly affected children and young adults with female predilection. Eight of 10 patients experienced recurrence, underscoring the aggressive nature of this disease. We suggest recognizing a new molecular subgroup of spinal astroblastoma and recommend testing newly diagnosed infratentorial astroblastomas for Ewing sarcoma RNA-binding protein 1-BEND2 fusion.

Expanding the Molecular Spectrum of Carcinoma Ex Pleomorphic Adenoma: An Analysis of 84 Cases With a Novel HMGA2::LINC02389 Fusion

Carcinoma ex pleomorphic adenoma (CXPA) is an aggressive epithelial and/or myoepithelial neoplasm that arises in association with a pleomorphic adenoma (PA). Its etiopathogenesis remains poorly understood, but it is believed that the development of this tumor is due to the accumulation of genetic, protein, metabolic, and epigenetic alterations in a PA. A retrospective review of the Salivary Gland Tumor Registry in Pilsen yielded 84 CXPA, namely 25/84 salivary duct carcinoma (SDC), 15/84 myoepithelial carcinoma (MC), 1/84 epithelial-myoepithelial carcinoma (EMC), and 1/84 adenoid cystic carcinoma (AdCC). All 84 CXPA cases were analyzed by next-generation sequencing (NGS) and/or fluorescence in situ hybridization (FISH). Forty-three tumors originally diagnosed as CXPA (43/84, 51.2%) showed some molecular alteration. Fusion transcripts were identified in 12/16 (75%) CXPA, including LIFR::PLAG1, CTNNB1::PLAG1, FGFR1::PLAG1, and a novel fusion, HMGA2::LINC02389. Most of the fusions were confirmed by FISH using PLAG1 (6/11) and HMGA2 (1/1) gene break probes. Split signals indicating gene break were identified by FISH for PLAG1 (12/17), HMGA2 (3/4), EWSR1 (7/22), and MYB (2/7). Concerning pathogenic mutations, only CXPA with epithelial differentiation (SDC) presented these alterations, including HRAS mutation (2/4), TP53 (1/4), PTEN (1/4), and ATK1 (1/4). In addition, amplifications in ERBB2 (17/35), MDM2 (1/4), and EWSR1 (1/7) were detected. A novel finding was the discovery of an HMGA2::LINC02389 fusion in 1 patient with EMC ex-PA. The present results indicate that molecular profiling of CXPA with myoepithelial differentiation (MC) tends to reveal chromosomal fusion events, whereas CXPA with epithelial differentiation (SDC) tends to have a higher frequency of pathogenic mutations and gene amplifications.

Molecularly Defined Thoracic Neoplasms

Molecularly defined neoplasms are increasingly recognized, given the broader application and performance of molecular studies. These studies allow us to better characterize these neoplasms and learn about their pathogenesis. In the thorax, molecularly defined neoplasms include tumors such as NUT carcinoma, SMARCA4-deficient undifferentiated tumor (DUT), primary pulmonary myxoid sarcoma with EWSR1::CREB1 fusion, hyalinizing clear cell carcinoma, and SMARCB1-deficient neoplasms. Overall, these tumors are rare but are now more often recognized given more widely available immunostains such as NUT (NUT carcinoma), BRG1 (SMARCA4-DUT), and INI-1 (SMARCB1-deficient neoplasm). Furthermore, cytogenetic studies for EWSR1 to support a hyalinizing clear cell carcinoma or primary pulmonary myxoid sarcoma are, in general, easily accessible. This enables pathologists to recognize and diagnose these tumors. The diagnosis of these tumors is important for clinical management and treatment. For instance, clinical trials are available for patients with NUT carcinoma, SMARCA4-DUT, and SMACRB1-deficient neoplasms. Herein, our current knowledge of clinical, morphologic, immunophenotypic, and molecular features of NUT carcinomas, SMARCA4-DUT, primary pulmonary myxoid sarcomas, hyalinizing clear cell carcinoma, and SMARCB1-deficient neoplasms will be reviewed.

Superficial Neurocristic EWSR1::FLI1 Fusion Tumor: A Distinctive, Clinically Indolent, S100 Protein/SOX10-Positive Neoplasm

It is now understood that identical gene fusions may be shared by different entities. We report a distinctive neoplasm of the skin and subcutis, harboring the Ewing sarcoma-associated EWSR1::FLI1 fusion but differing otherwise from Ewing sarcoma. Slides and blocks for 5 cutaneous neoplasms coded as other than Ewing sarcoma and harboring EWSR1::FLI1 were retrieved. Immunohistochemical and molecular genetic results were abstracted from reports. Methylation profiling was performed. Clinical information was obtained. The tumors occurred in 4 men and 1 woman (median: 25 years of age; range: 19-69 years) and involved the skin/subcutis of the back (2), thigh, buttock, and chest wall (median: 2.4 cm; range: 1-11 cm). Two tumors were present "years" before coming to clinical attention. The lesions were multinodular and circumscribed and consisted of nests of bland, round cells admixed with hyalinized collagenous bands containing spindled cells. Hemorrhage and cystic change were often present; necrosis was absent. All were diffusely S100 protein/SOX10-positive; 4 of 5 were CD99-negative. One tested case was strongly positive for NKX2.2. A variety of other tested markers were either focally positive (glial fibrillary acidic protein, p63) or negative. Molecular genetic results were as follows: EWSR1 exon 7::FLI1 exon 8, EWSR1 exon 11::FLI1 exon 5, EWSR1 exon 11::FLI1 exon 6, EWSR1 exon 7::FLI1 exon 6, and EWSR1 exon 10::FLI1 exon 6. Methylation profiling (3 cases) showed these to form a unique cluster, distinct from Ewing sarcoma. All patients underwent excision with negative margins; one received 1 cycle of chemotherapy. Clinical follow-up showed all patients to be alive without disease (median: 17 months; range: 11-62 months). Despite similar gene fusions, the morphologic, immunohistochemical, epigenetic, and clinical features of these unique EWSR1::FLI1-fused neoplasms of the skin and subcutis differ substantially from Ewing sarcoma. Interestingly, EWSR1 rearrangements involved exons 10 or 11, only rarely seen in Ewing sarcoma, in a majority of cases. Superficial neurocristic EWSR1::FLI1 fusion tumors should be rigorously distinguished from true cutaneous Ewing sarcomas.

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.

Sarcomas with EWSR1::Non-ETS Fusion (EWSR1::NFATC2 and EWSR1::PATZ1)

The wide application of increasingly advanced molecular studies in routine clinical practice has allowed a detailed, albeit still incomplete, genetic subclassification of undifferentiated round cell sarcomas. The WHO classification continues to include provisional molecular entities, whose clinicopathologic features are in the early stages of evolution. This review focuses on the clinicopathologic, molecular, and prognostic features of undifferentiated round cell sarcomas with EWSR1/FUS::NFATC2 or EWSR1::PATZ1 fusions. Classic histopathologic findings, uncommon variations, and diagnostic pitfalls are addressed, along with the utility of recently developed immunohistochemical and molecular markers.

A Practical Approach to Small Round Cell Tumors Involving the Gastrointestinal Tract and Abdomen

Small round cell neoplasms are diagnostically challenging owing to their clinical and pathologic overlap, necessitating use of large immunopanels and molecular analysis. Ewing sarcomas (ES) are the most common, but EWSR1 is translocated in several diverse neoplasms, some with round cell morphology. Molecular advances enable classification of many tumors previously termed 'atypical ES'. The current WHO Classification includes two new undifferentiated round cell sarcomas (with CIC or BCOR alterations), and a group of sarcomas in which EWSR1 partners with non-Ewing family transcription factor genes. This article reviews the spectrum of small round cell sarcomas within the gastrointestinal tract and abdomen.

Primary angiomatoid fibrous histiocytoma of the mandible with EWSR1-ATF1 fusion in an adult patient: case report and review of literature

OBJECTIVE

We report our diagnosis of a rare case of primary angiomatoid fibrous histiocytoma in the mandible of a 42-year-old male using next-generation sequencing to detect disease-specific EWSR1-ATF1 fusion.

STUDY DESIGN

After the initial cone beam computerized tomography scan and reconstruction, we performed immunohistochemical staining and fluorescence in situ hybridization analysis on tissue samples to detect EWSR1 gene rearrangement. For the final diagnosis, we performed next-generation sequencing to detect disease-specific EWSR1-ATF1 fusion.

RESULTS

FISH analysis showed approximately 55% of tumor cells with mostly isolated red signals, as well as several split red-green signals, indicating the presence of EWSR1 gene rearrangement. Next-generation sequencing analysis identified an EWSR1 exon9-ATF1 exon4 fusion, a diagnostic biomarker of angiomatoid fibrous histiocytoma (AFH). Based on the findings, we diagnosed primary AFH derived from the mandible.

CONCLUSIONS

Next-generation sequencing is a powerful methodology for detecting disease-specific EWSR1-ATF1 fusion and diagnosing primary angiomatoid fibrous histiocytoma.

"E-MGNET": Extra-Enteric Malignant Gastrointestinal Neuroectodermal Tumor- A Clinicopathological and Molecular Genetic Study of 11 Cases

Malignant gastrointestinal neuroectodermal tumors (MGNET), also known as "gastrointestinal clear cell sarcoma-like tumor", are very rare, aggressive sarcomas characterized by enteric location, distinctive pathologic features, and EWSR1/FUS::ATF1/CREB1 fusions. Despite identical genetics, the clinicopathologic features of MGNET are otherwise quite different from clear cell sarcoma of soft parts (CCS). Only exceptional extra-enteric MGNET (E-MGNET) have been reported. We report a series of 11 E-MGNET, the largest to date. Cases diagnosed as MGNET and occurring in non-intestinal locations were retrieved. Clinical follow-up was obtained. The tumors occurred in 3 males and 8 females (14-70 years of age, median 33 years) and involved the soft tissues of the neck (3), shoulder (1), buttock (2), orbit (1), and tongue/parapharyngeal space (1), the urinary bladder (1) and the falciform ligament/liver (1). Tumors showed morphologic features of enteric MGNET (small, relatively uniform, round to ovoid cells with round, regular nuclei containing small nucleoli, growing in multinodular and vaguely lobular patterns, with solid, pseudoalveolar and pseudopapillary architecture). Immunohistochemical results were: S100 protein (11/11), SOX10 (11/11), synaptophysin (3/10), CD56 (7/9), CD117 (3/9), DOG1 (0/4), ALK (4/8), chromogranin A (0/10), HMB45 (0/11), Melan-A (0/11), tyrosinase (0/4), MiTF (0/11). NGS results were: EWSR1::ATF1 (7 cases), EWSR1::CREB1 (3 cases) and EWSR1::PBX1 (1 case). The EWSR1::PBX1-positive tumor was similar to other cases, including osteoclast-like giant cells, and negative for myoepithelial markers. Clinical follow-up (range: 10 to 70 months; median 34 months) showed 4 patients dead of disease (10.5, 12, 25 and 64 months after diagnosis), 1 patient alive with extensive metastases (43 months after diagnosis), 1 patient alive with persistent local disease (11 months after diagnosis), and 4 alive without disease (10, 47, 53 and 70 months after diagnosis). One case is too recent for follow-up. The clinicopathologic and molecular genetic features of rare E-MGNET are essentially identical to those occurring in intestinal locations. Otherwise-typical E-MGNET may harbor EWSR1::PBX1, a finding previously unreported in this tumor type. As in enteric locations, the behavior of E-MGNET is aggressive, with metastases and/or death from disease in at least 50% of patients. E-MGNET should be distinguished from CCS and other tumors with similar fusions. ALK expression appears to be a common feature of tumors harboring EWSR1/FUS::ATF1/CREB1 fusion but is unlikely to predict therapeutic response to ALK inhibition. Future advances in our understanding of these unusual tumors will hopefully lead to improved nomenclature.

Clear cell sarcoma: state-of-the art and perspectives

INTRODUCTION

Clear cell sarcoma (CCS) is an ultrarare soft tissue sarcoma (STS) with a poor prognosis due to its propensity to metastasize and its low chemosensitivity. The standard treatment of localized CCS consists of wide surgical excision with or without additive radiotherapy. However, unresectable CCS is generally treated with conventional systemic therapies available for treatment of STS despite the weak scientific evidence to support its use.

AREAS COVERED

In this review, we discuss the clinicopathologic characteristics of CSS, as well as the current treatment landscape and future therapeutic approaches.

EXPERT OPINION

The current treatment strategy of advanced CCSs, based on STSs regimens, shows a lack of effective options. Combination therapiesin particular, the association of immunotherapy and TKIs, represent a promising approach. Translational studies are needed in order to decipher the regulatory mechanisms involved in the oncogenesis of this ultrarare sarcoma and identify potential molecular targets.

Imaging and treatment with 68Gallium and 177Lutetium-DOTATATE in a rare SSTR2 and ESWR1-CREM fusion positive undifferentiated round cell tumour of the lung

The authors present a 45-year-old lady with a rare undifferentiated round cell tumour of the lung with a ESWR1-CREM fusion gene that progressed despite multiple lines of therapy. The tumour was Somatostatin Receptors Type 2 (SSTR2) positive and avid on ⁶⁸Gallium-DOTATATE imaging. This allowed for novel treatment with Peptide Receptor Radionuclide Therapy (PRRT) using ¹⁷⁷Lutetium-DOTATATE after all other standard of care options were exhausted.

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.

Maxillary clear cell odontogenic carcinoma with EWSR1-ATF1 fusion gene mimicking sclerosing odontogenic carcinoma: A case report and literature review

Both clear cell odontogenic carcinoma (CCOC) and sclerosing odontogenic carcinoma (SOC) are rare odontogenic malignancies. Here, we report a case of maxillary CCOC whose clinical and histologic features resembled those of SOC. Radiologically, the tumor presented as an ill-defined, expansile radiolucency with local bone destruction. Histologically, the tumor was comprised of thin cords or strands of odontogenic epithelium permeating through a sclerosed fibrous stroma with occasional clear cell foci. It damaged the cortical plates and invaded the adjacent soft tissue. Immunohistochemical expression of Pancytokeratin, Cytokeratin 19, p63, Cytokeratin 5/6, and Cytokeratin 14, as well as focal expression of Cytokeratin 7, demonstrated the epithelial nature of the tumor. Alcian Blue Periodic acid Schiff staining revealed a lack of intracellular mucin. Fluorescence in situ hybridization analysis revealed Ewing sarcoma RNA binding protein 1 and activating transcription factor 1 gene translocation, further confirming the diagnosis of CCOC. Lastly, we contextualized the genetic analysis of our case to that of CCOC in the literature.

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.

Identification of Hub Genes Associated With the Development of Stomach Adenocarcinoma by Integrated Bioinformatics Analysis

Objective

This study was conducted in order to gain a better understanding of the molecular mechanisms of stomach adenocarcinoma (STAD), which is necessary to predict the prognosis of STAD and develop novel gene therapy strategies.

Methods

In this study, the gene expression profile of GSE118916 in the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas Program (TCGA) was used to explore the differential co-expression genes of STAD and normal tissues.

Results

A total of 407 STAD samples were collected, consisting of 375 from stomach adenocarcinoma tissues and 32 from normal tissues, as well as RNA-seq count data for 19,600 genes. Forty-two differentially expressed genes were screened by weighted gene co-expression network analysis (WGCNA) and differentially expressed gene analysis. According to the functional annotation analysis of the clusterProfiler R package, these genes were analyzed for GO function enrichment, digestion (biological process), tube bottom material membrane (cell component), and oxidoreductase activity (molecular function). The KEGG pathway was enriched in gastric acid secretion and chemical carcinogenesis. In addition, Cytoscape's cytoHubba plug-in was used to identify seven hub genes (EWSR1, ESR1, CLTC, PCMT1, TP53, HUWE1, and HDAC1) in a protein-protein interaction (PPI) network consisting of 7 nodes and 11 edges. Compared with normal tissues, CLTC and TP53 genes were upregulated in stomach adenocarcinoma (P < 0.05). TP53 was expressed differently in stages II and IV, EWSR1 was expressed differently in stages II and III, and ESR1 was expressed differently in stages I-III. Among the seven hub genes, Kaplan-Meier analysis and TCGG showed that the expression levels of HDAC1 and CLTC were significantly correlated with OS in patients with stomach adenocarcinoma (P < 0.05). GEPIA2 analysis showed that ESR1 expression was closely correlated with OS and DFS in gastric adenocarcinoma (P < 0.05). Then, the expression of the genes and their correlations were revealed by the R2 Platform (http://r2.amc.nl). Finally, we collected 18 pairs of gastric mucosal tissues from normal people and cancer tissues from patients with stomach adenocarcinoma. The expression levels of the above seven hub genes and their relative protein expression were detected by RT-PCR and immunohistochemistry (IHC). The results showed that the gene and protein expression levels in stomach adenocarcinoma tissues were increased than those in the normal group.

Conclusion

In summary, we believe that the identified hub genes were related to the occurrence of stomach adenocarcinoma, especially the expression of ESR1, HDAC1, and CLTC genes, which are related to the prognosis and overall survival of patients and may become the potential for the future diagnosis and treatment of STAD.

Extraskeletal Ewing's Sarcoma with CD7 Positivity and T-cell Receptor/Immunoglobulin Rearrangement Masquerading as T-lymphoblastic Lymphoma

Background: Extraskeletal Ewing's Sarcoma (EES) may harbor more than one tumor-specific genetic abnormality, leading to diagnostic difficulties. Case report: We report a nine-year-old boy with recurrent mass of his right thigh. Tumor cells were round, with scant cytoplasm, finely dispersed chromatin, and inapparent, small nucleoli. The initial misdiagnosis was T-lymphoblastic lymphoma due to CD7 and TCR/Ig monoclonal rearrangement. As it expressed NKX2.2 and harbored an EWSR1-FLI1 fusion transcript, the diagnosis was changed to EES. The child underwent EES therapy with good initial response, but had a subcutaneous relapse at 22 months. Conclusion: In addition to typical genetic alterations, Ewing sarcoma can also express CD7 and TCR/Ig rearrangement, which are not limited to lymphoma.

EWSR1-ATF1 dependent 3D connectivity regulates oncogenic and differentiation programs in Clear Cell Sarcoma

Oncogenic fusion proteins generated by chromosomal translocations play major roles in cancer. Among them, fusions between EWSR1 and transcription factors generate oncogenes with powerful chromatin regulatory activities, capable of establishing complex gene expression programs in permissive precursor cells. Here we define the epigenetic and 3D connectivity landscape of Clear Cell Sarcoma, an aggressive cancer driven by the EWSR1-ATF1 fusion gene. We find that EWSR1-ATF1 displays a distinct DNA binding pattern that requires the EWSR1 domain and promotes ATF1 retargeting to new distal sites, leading to chromatin activation and the establishment of a 3D network that controls oncogenic and differentiation signatures observed in primary CCS tumors. Conversely, EWSR1-ATF1 depletion results in a marked reconfiguration of 3D connectivity, including the emergence of regulatory circuits that promote neural crest-related developmental programs. Taken together, our study elucidates the epigenetic mechanisms utilized by EWSR1-ATF1 to establish regulatory networks in CCS, and points to precursor cells in the neural crest lineage as candidate cells of origin for these tumors.

The relationship between cellular histogenesis and molecular phenotypes for the EWSR1- ATF1 fusion in clear cell sarcoma (CCS) requires further characterization. Here, the authors investigate the EWSR1-ATF1 gene regulation networks in CCS cell lines, primary tumors, and mesenchymal stem cells.

A Case Series of Metastatic Malignant Gastrointestinal Neuroectodermal Tumors and Comprehensive Genomic Profiling Analysis of 20 Cases

Malignant gastrointestinal neuroectodermal tumor (GNET) is an ultra-rare soft tissue sarcoma, therefore often misdiagnosed and has no available standard treatment. Here, we report 3 cases of metastatic GNET with variable clinical courses. Our small case series as well as extensive literature review, further support that GNET is a spectrum of diseases with variable inherent biology and prognosis. Surgical management in the setting of recurrent/metastatic disease may be appropriate for GNET with indolent nature. Response to systemic treatments including chemotherapy and targeted treatments is variable, likely related to heterogenous biology as well. Furthermore, we retrospectively identified 20 additional GNET cases from Foundation Medicine’s genomic database and expanded on their clinicopathological and genomic features. Comprehensive genomic profiling (CGP) with DNA and RNA sequencing of this cohort, in the course of clinical care, demonstrated recurrent EWSR1 chromosomal rearrangements and a sparsity of additional recurrent or driver genomic alterations. All cases had low tumor mutational burden (TMB) and were microsatellite stable.

Expanding the Spectrum of EWSR1-NFATC2-rearranged Benign Tumors: A Common Genomic Abnormality in Vascular Malformation/Hemangioma and Simple Bone Cyst

A simple bone cyst (SBC) is a cystic bone lesion predominantly affecting young males. The cyst is lined by a fibrous membrane and filled with serosanguinous fluid. EWSR1/FUS-NFATC2 rearrangements were recently identified in SBC. We here report exactly the same rearrangement in 3 lesions diagnosed as vascular malformations of 2 elderly patients. In total, through Archer FusionPlex, fluorescence in situ hybridization and/or reverse transcriptase-polymerase chain reaction the EWSR1-NFATC2 rearrangement was identified in 6 of 9 SBC, 3 of 12 benign vascular tumors, and none of 5 aneurysmal bone cyst lacking USP6 fusion. Using fluorescence in situ hybridization, it was apparent that amplification of the fusion, as seen in EWSR1-NFATC2 round cell sarcomas, was absent, and that in the vascular tumors the fusion was present both in the lining cells as well as in the surrounding spindle cells. Of note, not all of the spaces in the vascular malformations were lined by endothelial cells. Aggrecan was positive in all cases but was not specific. NKX2-2 and NKX3-1 staining were negative in all cases. Thus, even though the overlap between the 2 entities is limited to the presence of few thick-walled cysts lacking endothelial lining in the benign vascular malformations, the spectrum of benign tumors containing NFATC2 fusions should be expanded and contains not only SBC in the young, but also vascular malformation/hemangioma in elderly patients.

Recurrent fusions in PLAGL1 define a distinct subset of pediatric-type supratentorial neuroepithelial tumors

Ependymomas encompass a heterogeneous group of central nervous system (CNS) neoplasms that occur along the entire neuroaxis. In recent years, extensive (epi-)genomic profiling efforts have identified several molecular groups of ependymoma that are characterized by distinct molecular alterations and/or patterns. Based on unsupervised visualization of a large cohort of genome-wide DNA methylation data, we identified a highly distinct group of pediatric-type tumors (n = 40) forming a cluster separate from all established CNS tumor types, of which a high proportion were histopathologically diagnosed as ependymoma. RNA sequencing revealed recurrent fusions involving the pleomorphic adenoma gene-like 1 (PLAGL1) gene in 19 of 20 of the samples analyzed, with the most common fusion being EWSR1:PLAGL1 (n = 13). Five tumors showed a PLAGL1:FOXO1 fusion and one a PLAGL1:EP300 fusion. High transcript levels of PLAGL1 were noted in these tumors, with concurrent overexpression of the imprinted genes H19 and IGF2, which are regulated by PLAGL1. Histopathological review of cases with sufficient material (n = 16) demonstrated a broad morphological spectrum of tumors with predominant ependymoma-like features. Immunohistochemically, tumors were GFAP positive and OLIG2- and SOX10 negative. In 3/16 of the cases, a dot-like positivity for EMA was detected. All tumors in our series were located in the supratentorial compartment. Median age of the patients at the time of diagnosis was 6.2 years. Median progression-free survival was 35 months (for 11 patients with data available). In summary, our findings suggest the existence of a novel group of supratentorial neuroepithelial tumors that are characterized by recurrent PLAGL1 fusions and enriched for pediatric patients.

Fine-needle aspiration cytopathology of soft tissue myoepithelioma: an analysis of seven cases

INTRODUCTION

Soft tissue myoepithelioma (STM), a rare mesenchymal neoplasm morphologically analogous to its more common salivary gland (SG) counterpart, is the subject of single case reports regarding its fine-needle aspiration (FNA) biopsy. To our knowledge, ours is the first case series of STM.

MATERIALS AND METHODS

A search was made of our pathology databases for cases diagnosed as STM. FNA biopsy smears and cell blocks were performed using standard techniques.

RESULTS

Seven cases were retrieved from 4 men and 3 women (M:F = 1.3:1; age range: 25-79 years, x = 54 years). All but 1 presented as a primary neoplasm. Six aspirates were from the extremities, and 1 from the abdominal wall. Mean tumor size was 5.7 cm. Cytologic diagnosis of STM or suspicious for STM was made in 3 cases (43%). Remaining FNA diagnoses were spindle cell neoplasm/lesion (2), spindle cell sarcoma (1), and extraskeletal myxoid chondrosarcoma (1). Three cases were composed primarily or solely of uniform spindle cells, 3 primarily of uniform epithelioid cells with plasmacytoid features, and 1 case a mixture of these 2 cell types. Myxoid/chondromyxoid stroma was relatively abundant except in the single hypocellular example. Immunohistochemical (IHC) testing performed in 71% was nonspecific, but positive with S-100 in 4 of 5, EMA in 3 of 3, calponin in 2 of 2, and keratin in 1 of 3 examples.

CONCLUSION

FNA biopsy smears of STM are remarkably similar cytomorphologically to their SG equivalent. However, STM can be misidentified principally as extraskeletal myxoid chondrosarcoma, thus requiring a relatively broad IHC panel for a specific diagnosis.

FUS-CREM-rearranged malignant epithelioid neoplasm mimicking neuroendocrine neoplasm of unknown primary

A 76-year-old women presented with abdominal pain. Diagnostic investigations suggested peritoneal carcinomatosis. Histological examination of laparoscopic biopsies showed large epithelioid cells forming sheets intermingled with some lymphocytes. There was no clearly distinguishable stroma. Immunohistochemistry showed diffuse and strong expression of cytokeratin AE1/AE3, synaptophysin and chromogranin-A.

Undifferentiated sarcoma of bone with a round to epithelioid cell phenotype harboring a novel EWSR1-SSX2 fusion identified by RNA-based next-generation sequencing

Due to the increased application of RNA-based next-generation sequencing techniques on bone and soft tissue round cell sarcomas new fusions are frequently found, thereby expanding the molecular landscape of these tumors. In this report, we describe and discuss the finding of an undifferentiated sarcoma of the bone with a round to epithelioid cell phenotype harboring a novel EWSR1-SSX2 fusion. Treatment of this new bone tumor entity according to the Euro Ewing 2012 protocol led to complete pathologic response.

Gene fusions in vascular tumors and their underlying molecular mechanisms

INTRODUCTION

The group of vascular tumors contains many different entities, and is considered difficult by pathologists, as they often have overlapping histological characteristics. Chromosomal translocations have been identified in ~20% of mesenchymal tumors and are considered the drivers of tumor formation. Many translocations have been discovered over the past decade through next-generation sequencing. This technological advancement has also revealed several recurrent gene fusions in vascular tumors.

AREAS COVERED

This review will discuss the various vascular tumors for which recurrent gene fusions have been identified. The gene fusions and the presumed molecular mechanisms underlying tumorigenesis are shown, and potential implications for targeted therapies discussed. The identification of these gene fusions in vascular tumors has improved diagnostic accuracy, especially since several of these fusions can be easily detected using surrogate immunohistochemical markers.

EXPERT OPINION

The identification of gene fusions in a subset of vascular tumors over the past decade has improved diagnostic accuracy, and has provided the pathologists with novel diagnostic tools to accurately diagnose these often difficult tumors. Moreover, the increased understanding of the underlying molecular mechanisms can guide the development of targeted therapeutic strategies.

Intra-abdominal EWSR1/FUS-CREM-rearranged malignant epithelioid neoplasms: two cases of an emerging aggressive entity with emphasis on misleading immunophenotype

CREB family (CREB1, ATF1, and CREM) gene fusions are defining markers in diverse mesenchymal neoplasms (clear cell sarcoma, angiomatoid fibrous histiocytoma, and others). However, neoplasms harboring EWSR1-CREM/FUS-CREM fusions are rare and poorly characterized. We describe two cases (55-year-old male with 7.5 cm renal mass and 32-year-old female with 5.5 cm mesenteric mass) illustrating their misleading immunophenotypes. Histologically, both showed eosinophilic and focally clear epithelioid cells arranged into sheets, nests, and trabeculae. Immunohistochemistry showed ALK, EMA, and AE1/AE3 immunoreactivity suggesting ALK-rearranged renal cell carcinoma (Case 1) and coexpression of keratin, EMA, synaptophysin, and chromogranin-A, suggesting neuroendocrine neoplasm (Case 2). Targeted RNA sequencing revealed EWSR1-CREM (Case 1) and FUS-CREM (Case 2) fusions. These cases add to the spectrum of CREM fusion-positive intra-abdominal epithelioid neoplasms. Their unusual immunophenotype and unexpected sites represent major pitfalls, underline a wide differential diagnosis, and emphasize the value of molecular testing in correctly diagnosing them.

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

EWSR1 belongs to the FET family of RNA-binding proteins including also Fused in Sarcoma (FUS), and TATA-box binding protein Associated Factor 15 (TAF15). As consequence of the multifunctional role of EWSR1 leading to a high frequency of transcription of the chromosomal region where the gene is located, EWSR1 is exposed to aberrations such as rearrangements. Consecutive binding to other genes leads to chimeric proteins inducing oncogenesis. The other TET family members are homologous. With the advent of widely used modern molecular techniques during the last decades, it has become obvious that EWSR1 is involved in the development of diverse benign and malignant tumors with mesenchymal, neuroectodermal, and epithelial/myoepithelial features. As oncogenic transformation mediated by EWSR1-fusion proteins leads to such diverse tumor types, there must be a selection on the multipotent stem cell level. In this review, we will focus on the wide variety of soft tissue and bone entities, including benign and malignant lesions, harboring EWSR1 rearrangement. Fusion gene analysis is the diagnostic gold standard in most of these tumors. We present clinicopathologic, immunohistochemical, and molecular features and discuss differential diagnoses.

Multiscale-omic assessment of EWSR1-NFATc2 fusion positive sarcomas identifies the mTOR pathway as a potential therapeutic target

Sarcomas harboring EWSR1-NFATc2 fusions have historically been categorized and treated as Ewing sarcoma. Emerging evidence suggests unique molecular characteristics and chemotherapy sensitivities in EWSR1-NFATc2 fusion positive sarcomas. Comprehensive genomic profiles of 1024 EWSR1 fusion positive sarcomas, including 14 EWSR1-NFATc2 fusions, were identified in the FoundationCore® database. Additional data from the Gene Expression Omnibus, the Genomics of Drug Sensitivity in Cancer and The Cancer Genome Atlas datasets were included for analysis. EWSR1-NFATc2 fusion positive sarcomas were genomically distinct from traditional Ewing sarcoma and demonstrated upregulation of the mTOR pathway. We also present a case of a 58-year-old male patient with metastatic EWSR1-NFATc2 fusion positive sarcoma who achieved 47 months of disease stabilization when treated with combination mTOR and VEGF inhibition. EWSR1-NFATc2 fusion positive sarcomas are molecularly distinct entities with overactive mTOR signaling; which may be therapeutically targetable. These findings support the use of precision medicine in the Ewing family of tumors.

Clinicopathologic and Molecular Cytogenetic Analysis of 8 Cases With Uterine Cervical Ewing Sarcoma: Case Series With Literature Review

Ewing sarcoma (ES) is a highly malignant tumor that rarely occurs in the uterine cervix. Herein, we report 8 cases with ES arising primarily in the uterine cervix by focusing on clinicopathologic and molecular cytogenetic features and differential diagnoses. Eight cases of cervical ES were diagnosed between February, 2012, and September, 2018. The age of patients ranged from 13 to 47 years. Abnormal vaginal bleeding and lower abdominal pain were the most common symptoms. Histologically, the tumor was composed of uniform, round, and oval cells with a narrow rim of eosinophilic cytoplasm. Fibrous septa were observed between tumor cell nests. The tumors showed brisk mitotic activity and areas of coagulative necrosis. According to immunohistochemical studies, 50% (4/8) of the cases were positive for cytokeratin (AE1/AE3), and 87.5% (7/8) were positive for synaptophysin, which resulted in a diagnostic confusion with small cell carcinoma, primarily when dealing with small cervical biopsies. Molecular testing demonstrated the rearrangement of the EWSR1 gene in all of the 8 cases, which confirmed the diagnosis of ES. Although rare, ES should be considered as indicators of cervical small round cell neoplasms. Molecular analysis may greatly contribute to the final diagnosis of ES occurring in this unusual location.

Presentation of a rare, highly aggressive peritoneal disease: desmoplastic small round cell tumor and its therapeutic options

Background

Desmoplastic small round cell tumor is a rare highly aggressive peritoneal disease (sarcoma) with mortality rates up to 70% in the first 3 years after diagnosis. It mainly affects young men. Patients clinically complain about diffuse abdominal pain.

Methods

This case report describes the clinical course of a 69-year-old man who presented with recurrent abdominal pain. Physical examination, laboratory testing, imaging, and gastroscopy were performed. Intra-abdominal peritoneal biopsies were taken during diagnostic laparoscopy.

Results

Physical examination was unremarkable. Laboratory results showed elevated white blood cells, C‑reactive protein, and negative tumor markers. Computed tomography and positron emission tomography scan revealed extensive peritoneal metastases with diffuse intra-abdominal signal intensities and ascites. Gastroscopy was unremarkable, whereas diagnostic laparoscopy confirmed imaging results with a peritoneal cancer index of 39. Extensive immunohistochemical and consecutive molecular investigations led to the diagnosis of an intraperitoneal desmoplastic small round cell tumor.

Conclusion

Our case report demonstrates a very rare cause of recurrent abdominal pain. Desmoplastic small round cell tumor is a rare and highly aggressive undifferentiated sarcoma, which mainly affects young men. Treatment options include chemotherapy, radiotherapy, cytoreductive surgery, and/or hyperthermic intraperitoneal chemotherapy. Standardized treatment protocols are still lacking because only a few cases have been described so far. Differential diagnoses include all malignancies with peritoneal masses.

Molecular Pathology of Salivary Gland Neoplasms: Diagnostic, Prognostic, and Predictive Perspective

Salivary gland neoplasms are an uncommon and widely heterogeneous group of tumors. In recent years, there has been considerable progress in efforts to reveal the molecular landscape of these tumors, although it is still limited and appears to be only the tip of the iceberg. Genomic aberrations, especially specific chromosomal rearrangements including CRTC1-MAML2 and CRTC3-MAML2 in mucoepidermoid carcinoma, MYB-NFIB and MYBL1-NFIB fusions in adenoid cystic carcinoma, PLAG1 and HMGA2 alterations in pleomorphic adenoma and carcinoma ex pleomorphic adenoma, ETV6-NTRK3 and ETV6-RET in secretory carcinoma, EWSR1-ATF1 and EWSR1-CREM in clear cell carcinoma, provide new insights into the molecular pathogenesis of various salivary gland neoplasms and help to better classify them. These genetic aberrations primarily serve as diagnostic tools in salivary gland tumor diagnosis; however, some also have promise as prognostic or predictive biomarkers. This review summarizes the latest developments in molecular pathology of salivary gland tumors with a focus on distinctive molecular characteristics.

Sclerosing odontogenic carcinoma - review of all published cases: is it a justifiable addition as a malignancy?

INTRODUCTION

Sclerosing odontogenic carcinoma was a new addition to the list of head and neck tumors by World Health Organization in 2017. This lesion has scarcely been reported and a lack of pathognomonic markers for diagnosis exists.

OBJECTIVE

The aim of the study was to summarize findings from the available literature to provide up-to-date information on sclerosing odontogenic carcinoma and to analyse clinical, radiological, and histopathological features to obtain information for and against as an odontogenic malignancy.

METHODS

We conducted a comprehensive review of literature by searching Pubmed, EBSCO and Web of Science databases, according to PRISMA guidelines. All the cases reported as sclerosing odontogenic carcinoma in English were included. Data retrieved from the articles were gender, age, clinical features, site, relevant medical history, radiographical findings, histopathological findings, immunohistochemical findings, treatments provided and prognosis.

RESULTS

Mean age at diagnosis of sclerosing odontogenic carcinoma was 54.4 years with a very slight female predilection. Sclerosing odontogenic carcinoma was commonly reported in the mandible as an expansile swelling which can be asymptomatic or associated with pain or paraesthesia. They appeared radiolucent with cortical resorption in radiograph evaluation. Histologically, sclerosing odontogenic carcinoma was composed of epithelioid cells in dense, fibrous, or sclerotic stroma with equivocal perineural invasion. Mild cellular atypia and inconspicuous mitotic activity were observed. There is no specific immunohistochemical marker for sclerosing odontogenic carcinoma. AE1/AE3, CK 5/6, CK 14, CK19, p63 and E-cadherin were the widely expressed markers for sclerosing odontogenic carcinoma. Surgical resection was the main treatment provided with no recurrence in most cases. No cases of metastasis were reported.

CONCLUSION

From the literature available, sclerosing odontogenic carcinoma is justifiable as a malignant tumor with no or unknown metastatic potential which can be adequately treated with surgical resection. However, there is insufficient evidence for histological grading or degree of malignancy of this tumor.

Distinct clinicopathological features of pulmonary primary angiomatoid fibrous histiocytoma: A report of four new cases and review of the literature

BACKGROUND

The aim of this study was to highlight the clinicopathological features of pulmonary primary angiomatoid fibrous histiocytoma (PPAFH) to assist with a differential diagnosis.

METHODS

There were 10 previous reports in the literature and four new PPAFH cases reviewed in this study. Immunohistochemistry (IHC), fluorescence in situ hybridization (FISH) and DNA and RNA-based next-generation sequencing (NGS) was performed in the four new cases reported here.

RESULTS

In the four new PPAFH cases, the ages of occurrence were in patients age from 33 to 55 years and tumor sizes were from 1.5 to 8 cm. Three of four (75.0%) tumors were located in the endobronchus. The most common morphological changes included delineated fibrous capsule (100%, 4/4), lymphoplasmacytic cuff (100%, 4/4), and dense or richly lymphoplasmatic infiltration (100%, 4/4). IHC analysis revealed that the tumor cells of four cases expressed vimentin and TLE1, ALK and CD163 or CD68 was positive in three cases, epithelial membrane antigen (EMA), desmin was positive in two cases, and SMA focal positive expression was observed in two cases. EWSR1 gene rearrangement was positive in all PPAFH cases (100%, 4/4) by FISH detections and four cases were confirmed as EWSR1-CREB1 fusion variant by DNA and RNA based NGS. No regional lymph nodes and distal metastasis, recurrences and death of disease after surgical excision were recorded in all four cases.

CONCLUSIONS

PPAFH is a very unusual pulmonary primary mesenchymal tumor and the clinicopathological features are like other unusual sites counterparts, but with a smaller tumor size, related with large airway, with a tendency to exhibit benign biological behavior, with EWSR1 gene rearrangement and higher frequency of EWSR1-CREB1 gene fusion.

KEY POINTS

Significant findings in the study: In comparison with "classic somatic" and nonpulmonary visceral angiomatoid fibrous histiocytoma, pulmonary primary angiomatoid fibrous histiocytoma display distinct clinicopathological features and prognosis. What this study adds The study provided the pathological differential diagnostic criteria and clinico-pathological features for pulmonary primary angiomatoid fibrous histiocytoma.

EWSR1-SMAD3 fibroblastic tumour of bone: expanding the clinical spectrum

EWSR1-SMAD3 fibroblastic tumour is a recently described soft tissue lesion. To date, eight cases have been reported, all sited in superficial soft tissue, typically occurring in the hands and feet with a tendency for local recurrence if incompletely excised. No metastatic spread has been reported, and hence, these tumours are currently considered benign. Herein, we present the radiological and histological features of the first reported occurrence of this entity in bone: a 44-year-old man with a tumour in the right tibia, treated with en bloc resection and showing no signs of relapse at 7 years. This tumour should be added to the differential diagnosis of bone lesions which harbour EWSR1 gene rearrangement.

[Angiomatoid fibrous histiocytoma: a literature review and a report of two cases]

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor of intermediate malignancy potential, which predominantly affects children and young adults. This paper describes two cases of AFH, as well as a review of literature during 1979 to 2021. It gives data on the epidemiology, clinical features, diagnosis, and genetic characteristics of AFH.

Recent updates in the diagnosis of soft tissue tumors: Newly described tumor entities, newer immunohistochemical and genetic markers, concepts, including "inter-tumor relationships"

During the last two decades, there have been significant strides in the diagnosis of soft tissue tumors, including identification of various tumor entities, newer immunohistochemical markers, and an increasing number of molecular signatures, defining certain tumors. Lately, there are certain emerging tumor entities, defined by their molecular features with an impact on treatment. At the same time, there is a certain degree of overlap in the expression of certain immunohistochemical antibody markers, as well as genetic markers, with certain gene rearrangements and chimeric fusions observed among completely different tumors. Moreover, a certain amount of clinicopathological, immunohistochemical, and molecular proximity has been unraveled among certain tumor types. Over the years, the World Health Organization (WHO) fascicles on tumors of soft tissue have succinctly brought out these aspects. The present review describes recent updates in the diagnosis of soft tissue tumors, including certain newly described tumor entities; emphasizing upon newer, specific immunohistochemical and molecular markers, along with concepts, regarding "intertumor relationships".

Desmoplastic Small Round Cell Tumors: A review with focus on clinical management and therapeutic options

Desmoplastic Small Round Cell Tumors (DSRCTs) are an entity of rare, aggressive soft tissue sarcomas described by Gerald and Rosai in 1989. It predominantly affects male adolescents and young adults, with a peak incidence between an age of 20 and 30 years. Typically, DSRCT demonstrate as multiple small tumor nodules within the abdominal cave, retroperitoneum and pelvis. In more than 50% of the cases, the neoplasm presents metastatic at the timepoint of diagnosis. Histologically, DSRCTs have a characteristic morphology with sharply demarcated islands of uniform small round cells in abundant desmoplastic stroma organized in loose extracellular matrix. Immunohistochemistry reveals a polyphenotypic differentiation with co-expression of epithelial, myogenic, mesenchymal and neural markers. The morphology is highly variable and can hinder diagnosis. The most consistent molecular characteristic of DSRCT is the reciprocal t(11;22)(p13q12) translocation. This mutation leads to a formation of the EWSR1-WT1 fusion oncogene, which encodes for a chimeric protein with transcriptional regulatory activity and is regarded as driving source of the disease. To date, there is no standardized concept for clinical management, staging and treatment. Patients receive an aggressive multimodal therapeutic approach consisting of chemotherapy, radical surgical procedures, hyperthermic, intraperitoneal chemotherapy (HIPEC) and radiation. New targeted therapies are used in experimental settings as salvage therapy. So far, none of these therapies showed significant long-term success. This review gives an overview of diagnostic difficulties and pitfalls, discusses therapeutic strategies and highlights options for clinical management.

Primary Pulmonary Myxoid Sarcoma and Myxoid Angiomatoid Fibrous Histiocytoma: A Unifying Continuum With Shared and Distinct Features

Primary pulmonary myxoid sarcoma (PPMS) is a recently reported, exceedingly rare low-grade lung neoplasm characterized by reticular/lace-like growth of spindle to epithelioid cells embedded in an abundant myxoid matrix. Morphologically, it overlaps with a myxoid variant of angiomatoid fibrous histiocytoma (AFH) of the soft tissue. Genetically, they were both reported to harbor EWSR1-CREB1 fusion, while EWSR1-ATF1 has only been reported in AFH thus far. We report a case of primary pulmonary low-grade myxoid spindle cell tumor with morphologic and immunohistochemical features of PPMS but with an EWSR1-ATF1 fusion gene. In addition, we also encountered a case of endobronchial AFH with EWSR1-CREB1 translocation but also focal morphologic features of PPMS. These findings provide new evidence supporting the concept that PPMS and a myxoid variant of AFH represent a continuum with overlapping histologic, immunohistochemical, and genetic features.

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.

The spectrum of rare central nervous system (CNS) tumors with EWSR1-non-ETS fusions: experience from three pediatric institutions with review of the literature

The group of CNS mesenchymal (non‐meningothelial) and primary glial/neuronal tumors in association with EWSR1‐non‐ETS rearrangements comprises a growing spectrum of entities, mostly reported in isolation with incomplete molecular profiling. Archival files from three pediatric institutions were queried for unusual cases of pediatric (≤21 years) CNS EWSR1‐rearranged tumors confirmed by at least one molecular technique. Extra‐axial tumors and cases with a diagnosis of Ewing sarcoma (EWSR1‐ETS family fusions) were excluded. Additional studies, including anchored multiplex‐PCR with next‐generation sequencing and DNA methylation profiling, were performed as needed to determine fusion partner status and brain tumor methylation class, respectively. Five cases (median 17 years) were identified (M:F of 3:2). Location was parenchymal (n = 3) and undetermined (n = 2) with topographic distributions including posterior fossa (n = 1), frontal (n = 1), temporal (n = 1), parietal (n = 1) and occipital (n = 1) lobes. Final designation with fusion findings included desmoplastic small round cell tumor (EWSR1‐WT1; n = 1) and tumors of uncertain histogenesis (EWSR1‐CREM, n = 1; EWSR1‐CREB1, n = 1; EWSR1‐PLAGL1, n = 1; and EWSR1‐PATZ1, n = 1). Tumors showed a wide spectrum of morphology and biologic behavior. For EWSR1‐CREM, EWSR1‐PLAGL1 and EWSR1‐PATZ1 tumors, no significant methylation scores were reached in the known brain tumor classes. Available outcome (4/5) was reported as favorable (n = 2) and unfavorable (n = 2) with a median follow‐up of 30 months. In conclusion, we describe five primary EWSR1‐non‐ETS fused CNS tumors exhibiting morphologic and biologic heterogeneity and we highlight the clinical importance of determining specific fusion partners to improve diagnostic accuracy, treatment and monitoring. Larger prospective clinicopathological and molecular studies are needed to determine the prognostic implications of histotypes, anatomical location, fusion partners, breakpoints and methylation profiles in patients with these rare tumors.

EWSR1 overexpression is a pro-oncogenic event in multiple myeloma

Multiple myeloma (MM) is cytogenetically, genetically and molecularly heterogenous even among subclones in one patient, therefore, it is essential to identify both frequent and patient-specific drivers of molecular abnormality. Following previous molecular investigations, we in this study investigated the expression patterns and function of the Ewing sarcoma breakpoint region 1 (EWSR1) gene in MM. The EWSR1 transcriptional level in CD138-positive myeloma cells was higher in 36.4% of monoclonal gammopathy of undetermined significance, in 67.4% of MM patients compared with normal plasma cells, and significantly higher in ten human myeloma-derived cell lines (HMCLs) examined. EWSR1 gene knockdown caused growth inhibition with an increase of apoptotic cells in NCI-H929 and KMS-12-BM cells. Gene expression profiling using microarray analysis suggested EWSR1 gene knockdown caused transcriptional modulation of several genes associated with processes such as cell proliferation, cell motility, cell metabolism, and gene expression. Of particular, EWSR1 gene knockdown caused upregulation of let-7c and downregulation of its known targets K-RAS and AKT. Finally, our analysis using community database suggested that high EWSR1 expression positively associates with poor prognosis and advanced disease stage in MM. These findings suggest that EWSR1 overexpression is a pro-oncogenic molecular abnormality that may participate in MM progression.

DICER1-associated metastatic abdominopelvic primitive neuroectodermal tumor with an EWSR1 rearrangement in a 16-yr-old female

We report a case of a DICER1-associated EWSR1-rearranged malignant primitive neuroectodermal tumor (PNET) arising in a patient with DICER1 tumor predisposition syndrome. A 16-yr-old female with a history of multinodular goiter presented with a widely metastatic abdominal small round blue cell tumor with neuroectodermal differentiation. EWSR1 gene rearrangement was identified in the tumor by fluorescence in situ hybridization (FISH). Genetic analysis revealed biallelic pathogenic DICER1 variation. The patient was treated with an aggressive course of chemotherapy, surgery, and radiation with complete pathologic response. We believe this case to represent a new expression of the DICER1 tumor predisposition syndrome, an entity caused by deleterious germline mutations in the DICER1 gene, encoding a ribonuclease active in the processing of miRNA. Patients with germline mutations in DICER1 develop a diverse group of benign and malignant tumors. Some of these tumors have been noted to have immature neuroepithelium as a component, including the ciliary body medulloepithelioma and the recently described DICER1-associated presacral malignant teratoid neoplasm. To our knowledge, abdominal sarcomas that resemble PNET histology with an EWSR1 rearrangement have not previously been described as a classical expression of the DICER1 syndrome phenotype.

Extraskeletal myxoid chondrosarcoma: combining cytopathology with molecular testing to achieve diagnostic accuracy

INTRODUCTION

Advances in the genetics of soft tissue neoplasia have allowed for the diagnostic recognition of specific tumor types from small biopsy specimens, including those procured using the fine needle aspiration (FNA) biopsy technique. Extraskeletal myxoid chondrosarcoma (EMC) is a malignant mesenchymal neoplasm characterized by NR4A3 and, less specifically, by EWSR1 gene rearrangements. A series of EMC cytologic specimens was examined to demonstrate the diagnostic value of incorporating fluorescence in situ hybridization (FISH) testing in cytologic cases of suspected EMC.

MATERIALS AND METHODS

A search was made of our cytopathology and surgical pathology databases for cases diagnosed as EMC. FNA biopsy cytology, exfoliative cytology, imprint cytology, and FISH analysis were performed and examined using standard techniques.

RESULTS

A total of 16 cases of EMC were retrieved from 15 patients (male/female ratio, 2.8:1; mean age, 62 years). Of the 15 patients, 10 were new patients with primary tumors, 2 had locally recurrent tumors, and 4 had metastases. The sites included the extremities in 10 cases, the trunk in 4, serous effusion in 1, and a mediastinal lymph node in 1 case. The specific cytologic diagnoses were EMC (14 cases; 88%), suspicious for EMC (n = 1), and malignant cells (n = 1). All cases for which FISH testing was successfully used were specifically recognized as EMC. Aspirates and imprint smears consisted of uniformly rounded cells set in an opaque myxoid/chondromyxoid stroma (less abundant and more diaphanous in the effusion sample), sometimes arranged in short anastomosing cords. FNA of 1 case of an EMC cellular variant mimicked a malignant small rounded cell tumor.

CONCLUSION

EMC can be added to the growing list of soft tissue neoplasms that are specifically recognizable using cytopathology, coupled with judicious application of ancillary molecular testing.

Primary Intracranial Mesenchymal Tumor with EWSR1-CREM Gene Fusion: A Case Report and Literature Review

BACKGROUND

The prevalence of gene translocation in some mesenchymal tumors can be used as highly specific molecular diagnostic markers in clinic and pathology. EWSR1 is a partner gene in a large, diverse range of mesenchymal tumors.

CASE DESCRIPTION

This paper describes the case of a 31-year-old man who was diagnosed with a primary intracranial mesenchymal tumor with EWSR1-CREM gene fusion and eventually returned to a normal live with no signs of tumor recurrence or metastasis after treatment, including surgery therapy, radiotherapy, and 6 cycles of vincristine-doxorubicin-cyclophosphamide chemotherapy, even though the classification and grade of the tumor are still controversial.

CONCLUSIONS

This case is a novel entity of intracranial mesenchymal neoplasm with EWSR1-CREM gene fusion which was confirmed by histopathology, molecular pathology, and next-generation sequencing (NGS). The literature review shows only 5 cases of intracranial tumor harboring EWSR1-CREM gene fusion with similar features. With the further application of molecular pathology and NGS in clinical practice, there will be more intracranial mesenchymal tumor cases with EWSR1-CREM gene fusion found in the future, which may lead to further understanding of the diagnosis and clinical features of this neoplasm.

Subcutaneous desmoplastic small round-cell tumor: An unusual primary location expanding the differential of superficial round-cell tumors

Desmoplastic small round-cell tumor (DSRCT) is a rare, aggressive malignant tumor, which in the great majority of cases arises at abdominal-pelvic sites. Nevertheless, rare cases of primary extra-abdominal tumors have been reported. In challenging cases, its molecular hallmark, the EWSR1-WT1 reciprocal translocation, can be exploited diagnostically by various molecular techniques. Herein, we report an extremely rare case of primary subcutaneous DSRCT in an effort to raise awareness among our dermatopathology colleagues by expanding the differential of superficial round-cell tumors.