Malignant Gastrointestinal Neuroectodermal Tumor: Clinicopathologic, Immunohistochemical, and Molecular Analysis of 19 Cases

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.

Non-gastrointestinal stromal tumor, mesenchymal neoplasms of the gastrointestinal tract: a review of tumor genetics, pathology, and cross-sectional imaging findings

There is a diverse group of non-gastrointestinal stromal tumor (GIST), mesenchymal neoplasms of the gastrointestinal (GI) tract that demonstrate characteristic pathology and histogenesis as well as variable imaging findings and biological behavior. Recent advancements in tumor genetics have unveiled specific abnormalities associated with certain tumors, influencing their molecular pathogenesis, biology, response to treatment, and prognosis. Notably, giant fibrovascular polyps of the esophagus, identified through MDM2 gene amplifications, are now classified as liposarcomas. Some tumors exhibit distinctive patterns of disease distribution. Glomus tumors and plexiform fibromyxomas exhibit a pronounced affinity for the gastric antrum. In contrast, smooth muscle tumors within the GI tract are predominantly found in the esophagus and colorectum, surpassing the incidence of GISTs in these locations. Surgical resection suffices for symptomatic benign tumors; multimodality treatment may be necessary for frank sarcomas. This article aims to elucidate the cross-sectional imaging findings associated with a wide spectrum of these tumors, providing insights that align with their histopathological features.

Malignant Gastrointestinal Neuroectodermal Tumor of Small Intestine Showing DOG1 Expression: A Case Report and Review of Literature

Malignant gastrointestinal neuroectodermal tumor (GNET), also referred to as clear cell sarcoma-like tumor of the GI tract is a rare mesenchymal tumor of the gastrointestinal tract. It has to be distinguished from various mimickers including gastrointestinal stromal tumor (GIST) due to its aggressive course and different natural history and therapeutic approach. Here we report a case of GNET arising in the small intestine with aberrant DOG1 expression posing a diagnostic challenge. In this context, the combination of clinical, histomorphological, immunohistochemical, and molecular features helped to establish a proper diagnosis.

Small Intestine Gastrointestinal Clear Cell Sarcoma: A Case Report and Review of the Literature

Gastrointestinal clear cell sarcoma (GICCS)/malignant gastrointestinal neuroectodermal tumor (GNET) is an extremely rare form of cancer with aggressive clinical behavior. It has distinct pathological, immunohistochemical, ultrastructural, and molecular features. Herein, we present the case of a 20-year-old woman with no notable medical history who presented to the outpatient department with complaints of abdominal pain and vomiting. Symptoms had been evolving for 3 months. The physical examination revealed slight abdominal tenderness and melena. Biological investigations revealed iron-deficiency anemia. The upper and lower endoscopies showed no abnormalities. Magnetic resonance enterography revealed small bowel wall thickening of 15 mm × 2 mm. Exploratory laparotomy revealed an ileal mass with mesenteric lymphadenopathy. A wide resection of the mass was then performed. The final pathological report confirmed the diagnosis of small bowel GICCS/GNET. After 11 months of follow-up, the patient presented with mesenteric lymph node metastases.

Malignant gastrointestinal neuroectodermal tumor: a case report and literature review

Introduction and importance

A malignant gastrointestinal neuroectodermal tumor (GNET) is an extremely rare primary malignant mesenchymal tumor of the gastrointestinal tract characterized by EWSR1 gene rearrangement. An optimal systemic treatment strategy for advanced/recurrent GNET has not yet been identified.

Case presentation

A 24-year-old male patient was hospitalized with abdominal pain and underwent two operations for a tumor in his small intestine. Immunohistochemistry (IHC) showed strong expression of S-100 protein and SOX 10. Fluorescence in situ hybridization analysis and next-generation sequencing analysis indicated that there were EWSR gene rearrangements and the presence of EWSR-ATP1 gene fusions, respectively. The diagnosis of GNET in the small intestine was confirmed by pathology. The young patient received the fifth-line of apatinib mesylate and the sixth-line of apatinib combined with temozolomide. The two apatinib-containing regimens showed stable disease and progression-free survival of 4.7 months and 3.1 months with single-agent apatinib or apatinib combined with temozolomide, respectively.

Clinical discussion

To our best knowledge, this is the first report of malignant GNET treated with apatinib and temozolomide. Apatinib-containing regimens might has antineoplastic activity against GNET. The authors reviewed the relevant reports of previous GNET treatment, summarized the clinicopathological characteristics of GNET, and found that there are no reports of apatinib for backline treatment of GNET.

Conclusion

Containing apatinib may provide an additional treatment option for patients with chemotherapy-resistant GNET tumors.

The Malignant Gastrointestinal Neuroectodermal Tumor (GNET): A Distinct Entity and the Challenging Differential Diagnosis with Mesenchymal, Lymphoid, and Melanic Tumors: A Case Report and Brief Review of the Literature

(1) Background: A malignant gastrointestinal neuroectodermal tumor (GNET) is an ultra-rare primary neoplasm with a distinctive histopathological, immunohistochemical, molecular, and ultramicroscopic profile, synonymous terminology with clear cell sarcoma-like tumor of the gastrointestinal tract. This case report aims to describe a case of GNET with challenging mesenchymal, lymphoid, and melanic tumor differential diagnosis. (2) Case presentation: We discuss the case of a 67-year-old male patient who presented with diffuse abdominal pain, intermittent lack of intestinal transit, and frequent episodes of nausea, followed by segmental resection of the jejunum and sigmoid colon. The patient had no relevant medical history. The surgical specimen underwent immunohistochemical staining and morphological evaluation. (3) Results: Histopathological analysis reveals a moderately homogeneous polyhedral-epithelioid and spindle cell neoplastic proliferation with a zonal discohesive pattern and extensive and focal fasciculated architecture. Twenty monoclonal antibodies were used for immunostaining, which allowed GNET to be diagnosed on the basis of the tumoral immune profile, characterized by positive reactivity of S100, SOX10, and CD 56. (4) Conclusions: The poor prognosis of GNET is highlighted in the present study, along with the vital importance of differential diagnosis issues with mesenchymal, lymphoid, and melanic tumors, which make the diagnosis difficult for both pathologists and clinicians.

[Malignant gastrointestinal neuroectodermal tumor: A report of 2 cases and a review of the literature]

Malignant gastrointestinal neuroectodermal tumour (GNET) is an extremely rare neoplasm first described by Zambrano in 2003 as clear cell sarcoma like tumor of the gastrointestinal tract. In contrast to clear cell sarcoma, it has giant osteoclast cells and shows diffuse and intense positivity for S-100 with no immunohistochemical or ultrastructural melanocyte differentiation. We present the first cases of GNET reported in South America, occurring in Peru. Two cases of GNET, one in a female and one in a male, both between 60 and 70 years of age, were referred to our hospital for reevaluation. One underwent further treatment in our centre, but with an unfavourable evolution. Pathologists should be aware of the diagnostic criteria for GNET in order to avoid misdiagnosis due to confusion with other non-epithelial gastrointestinal neoplasms.

Case Report: Submucosal gastroblastoma with a novel PTCH1::GLI2 gene fusion in a 58-year-old man

Gastroblastoma is a rare biphasic tumor of the stomach that generally presents in young patients. MALAT1-GLI1 gene fusion was considered to be the characteristic molecular alteration of this tumor in previous reports. Herein, we described a 58-year-old man with a mass mainly located in the submucosa of the stomach. Microscopic examination showed a biphasic morphology with the same immunohistochemical phenotype as gastroblastoma. Interestingly, a novel PTCH1::GLI2 fusion rather than MALAT1-GLI1 fusion was detected in the tumor by RNA-based next generation sequencing (NGS). This was the first report that demonstrated a novel PTCH1::GLI2 gene fusion in gastroblastoma, and thus expanded the molecular spectrum of this tumor. The underlying pathogenesis merits further investigation.

SWI/SNF Complex-deficient Undifferentiated Carcinoma of the Gastrointestinal Tract: Clinicopathologic Study of 30 Cases With an Emphasis on Variable Morphology, Immune Features, and the Prognostic Significance of Different SMARCA4 and SMARCA2 Subunit Deficiencies

Undifferentiated carcinoma of the gastrointestinal tract has variable rhabdoid features. Expression of switch/sucrose nonfermenting (SWI/SNF) complex subunits is reportedly lost in a portion of cases; however, the prognostic significance of this loss remains unknown. Herein, 30 undifferentiated carcinoma cases were assessed for the expression of 4 SWI/SNF complex subunits (SMARCB1, SMARCA2, SMARCA4, and ARID1A). Tumor origin sites comprised stomach (40.0%), large intestine (20.0%), small intestine (16.7%), lower esophagus and stomach fundus (13.3%), ileocecal junction (3.3%), rectum (3.3%), and pancreas (3.3%). The tumors were composed of epithelioid neoplastic cells arranged in diffuse solid or discohesive sheets, nests, cords, poor cohesive pseudoglandular, and trabecular patterns. Rhabdoid tumor cells were identified in 66.7% (20/30) of cases. In total, 29/30 (96.7%) showed complete loss of at least 1 SWI/SNF subunit: SMARCA4-/SMARCA2- (11), isolated SMARCA4- (2), SMARCA4-/SMARCA2 unknown (6), isolated SMARCA2- (7), SMARCA2-/ARID1A- (1), and isolated ARID1A- (2). Negative or decreased expression (≤10% positive) of pan-cytokeratin was observed in 58.6% (17/29) of cases. In addition, 66.7% (20/30) of patients were late-stage (III or IV), and 65.2% (15/23) of stage IIB to IV patients succumbed to the disease at a mean clinical follow-up of 12.7 months. Specifically, patients with loss of SMARCA4 expression had the worst overall survival (P=0.028) and disease-free survival (P=0.006) rates, compared with those with SMARCA4 expression. The loss or decreased expression of epithelial markers is thus common in SWI/SNF complex-deficient undifferentiated carcinoma of the gastrointestinal tract, and loss of SMARCA4 correlates with poor prognosis.

Malignant Gastrointestinal Neuroectodermal Tumor: A New Kid on the Block?

ABSTRACT

Also referred to as "osteoclast-rich, clear cell sarcoma-like tumor of the gastrointestinal tract (CCSLGT)," malignant gastrointestinal neuroectodermal tumor is a newly described, rare, aggressive sarcoma that commonly arises in the small bowel, stomach, and colon. Histogenesis is likely from an autonomous nervous system-related primitive cell of neural crest origin. The hallmark genetic finding of EWS-CREB1 or EWS-ATF1 fusion transcripts clinches the diagnosis. Annular constrictive lesions tend to be smaller, show homogenous contrast enhancement on computed tomography, and may present with bowel obstruction. Larger, expansile masses tend to be exophytic and show heterogeneous contrast enhancement. Surgical resection is the mainstay of treatment. Frequent recurrences, metastases, and death from disease in 75% of patients portend a poor prognosis. Targeted chemotherapy based on specific tumor pathways is being developed.

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.

Malignant Gastrointestinal Neuroectodermal Tumor in the Right Heart: A Report of an Extremely Rare Case Presenting With a Cardiac Mass

Malignant gastrointestinal neuroectodermal tumor (GNET) is an extremely rare soft tissue sarcoma and has been designated as a new entity recently. At present, GNET virtually exclusively occurs in the gastrointestinal tract. Here we report a case of extra-GNET that arose in the right heart. A 62-year-old male complained of chest distress and breathing difficulty while lying down at night for over 1 month at admission. The radiological findings revealed an occupying lesion involving the right atrium and the right ventricle without any abdominal abnormalities. The patient then underwent a surgical resection. Microscopically, neoplastic cells proliferated in the pattern of nests and sheets with fibrous separation. Focal areas with cellular dyscohesion imparted a vague pseudopapillary pattern. These tumor cells were small to medium in size with fine chromatin and predominantly pale eosinophilic cytoplasm. The nuclei were typically round to oval with somewhat irregular contours and contained small nucleoli. The mitotic figures were easily found. Immunohistochemically, the neoplastic cells were positive for S100 and SOX-10 but negative for HMB-45, A103, and CD99. EWSR1-AFTF1 rearrangement was detected by fluorescence in situ hybridization and further confirmed by whole-transcriptome sequence analysis. The patient had pulmonary metastasis 8 months later and soon died of the disease. The overall survival of the patient was 20 months. In summary, we reported an extremely rare case of cardiac GNET, indicating that the location of GNET should not be confined to the GI tract as initially defined. Due to the lack of a specific effective treatment and the occurrence of early metastasis, cardiac GNET conferred a poor prognosis. More clinical and experimental studies are warranted to better manage this disease in the future.

Synchronous Malignant Gastrointestinal Neuroectodermal Tumor and SMARCA4-Deficient Undifferentiated Carcinoma With Independent Origins in the Small Intestine: A Case Report

Background

Malignant gastrointestinal neuroectodermal tumor (GNET) is a rare malignant mesenchymal neoplasm that commonly arises in the small bowel, stomach or colon. Meanwhile, SMARCA4-deficient undifferentiated carcinoma is a rarely reported entity with highly aggressive behavior that may involve the ovary, lung, gastrointestinal (GI) tract, endometrium and other organs. To our knowledge, we describe for the first time, an extremely rare case of synchronous GNET and SMARCA4-deficient undifferentiated carcinoma with independent origins in the small intestine.

Case Presentation

A 46-year-old woman presented with multiple small intestine masses and underwent surgical resection. Two distinct entities, GNET and SMARCA4-deficient undifferentiated carcinoma, were identified. GNET was composed of epithelioid and spindle cells with clear or eosinophilic cytoplasm arranged in sheets, nest, papillary, fascicular, palisade, rosette like or pseudoalveolar pattern. The neoplastic cells were positive for S-100 and SOX-10. Ewing sarcoma breakpoint region 1 gene (EWSR1) rearrangement was confirmed by fluorescence in situ hybridization (FISH), and EWSR1-CREB1 fusion was revealed by next-generation sequencing (NGS). SMARCA4-deficient undifferentiated carcinoma was composed mainly of poorly adhesive rhabdoid cells with eosinophilic cytoplasm arranged in a diffuse pattern. Multifocal necrosis, brisk mitotic figures as well as multinucleated tumor cells were observed. The neoplastic cells diffusely expressed pancytokeratin and vimentin, and was negative for SMARCA4(BRG1). Frame shift mutation of SMARCA4 was detected by NGS.

Conclusions

This is the first report that GNET and SMARCA4-deficient undifferentiated carcinoma occurred simultaneously in the small intestine, with the latter showing multiple involvement of the jejunum and ileum. The potential mechanism underlying co-existence of these two rare malignancies is unknown and need further investigations and concern.

Mesenchymal/non-epithelial mimickers of neuroendocrine neoplasms with a focus on fusion gene-associated and SWI/SNF-deficient tumors

Mimickers of neuroendocrine neoplasms (NEN) include a number of important pitfall tumors. Here, we describe our experience with mesenchymal mimics of NENs to illustrate their spectrum and draw the attention particularly to a group of mesenchymal/non-epithelial neoplasms (MN) that combine epithelioid histology with neuroendocrine (NE-) features and peculiar genetic abnormalities. In a consultation series of 4498 cases collected between 2009 and 2021, 2099 neoplasms expressing synaptophysin and/or chromograninA were reviewed and analyzed. A total of 364 (18%) were diagnosed as non-NENs, while the remaining tumors were NEN. The group of mesenchymal/non-epithelial neoplasms with NE-features (MN-NE) included 31/364 (8%) cases. These mostly malignant neoplasms showed an epithelioid morphology. While all but one tumor expressed synaptophysin, mostly patchy, only 10/29 (34%) co-expressed chromograninA. A total of 13/31 (42%) of the MN-NE showed EWSR1-related gene fusions (6 Ewing sarcomas, 5 clear cell sarcomas, and 1 desmoplastic small round cell tumor, 1 neoplasm with FUS-CREM gene fusion) and 7 (23%) were SWI/SNF (SMARCB1 or SMARCA4)-deficient neoplasms. The remaining MN-NE included synovial sarcoma, sclerosing epithelioid mesenchymal neoplasm, melanoma, alveolar soft part sarcoma, solitary fibrous tumor, and chordoma. A total of 27/31 MN-NE were from the last 8 years, and 6 of them were located in the pancreas. Eleven MN-NE were initially diagnosed as neuroendocrine carcinomas (NECs). MN-NE with epithelioid features play an increasing role as mimickers of NECs. They mostly belong to tumors with gene fusions involving the EWSR1 gene, or with SWI/SNF complex deficiency. Synaptophysin expression is mostly patchy and chromograninA expression is infrequent in MN-NE of this series and data extracted from literature.

An integrative histopathological and epigenetic characterization of primary intracranial mesenchymal tumors, FET:CREB-fused broadening the spectrum of tumor entities in comparison with their soft tissue counterparts

FET:CREB fusions have been described in a variety of tumors from various phenotypes. Recently, these fusion transcripts were reported in intracranial tumors, variably named intracranial mesenchymal myxoid tumors or angiomatoid fibrous histiocytomas. Controversy remains concerning the terminology for these tumors. Here, we report 11 cases of central nervous system mesenchymal tumors with proven FET:CREB fusion. Most DNA methylation profiles were not classifiable using the Heidelberg Brain Tumor or Sarcoma Classifier (v11b4/v12.2). However, by using unsupervised t‐SNE and hierarchical clustering analyses, six of the cases constituted a distinct cluster. The remaining four tumors showed no obvious relation to any of the other referenced classes but were close to the clusters of extra‐CNS angiomatoid fibrous histiocytomas (n = 1), clear cell sarcomas (n = 1), or solitary fibrous tumors (n = 2). Our findings confirm that intracranial FET:CREB‐fused tumors do not represent a single molecular tumor entity, although most samples clustered close to each other, indicating the existence of a distinct epigenetic group that could potentially be partially masked by the low number of cases included. Further analyses are needed to characterize intracranial FET:CREB fused‐defined tumors in more detail.

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.

Anlotinib as a post-third-line therapy for the treatment of advanced nonsmall cell lung cancer

There is no standard treatment strategy for the third-line and above treatment of advanced nonsmall cell lung cancer (NSCLC). This study aimed to investigate the effects of anlotinib in patients with NSCLC. Data was collected from a group of advanced lung cancer patients who received anlotinib as a third-line or post-third-line treatment between 2017 and 2019. The Kaplan-Meier method was used to calculate the progression-free survival (PFS) of these lung cancer patients treated with anlotinib. Univariate analysis was performed using the log-rank test. Forest plot was used for subgroup analysis.Our study included 44 patients. Oral anlotinib was used as a third-line treatment to treat 26 patients, and as a fourth-line or multiline treatment in 18 patients. The objective control rate was 5%, the disease control rate was 89%, and the median PFS was 4.0 months with a 95% confidence interval. Common toxicities included anorexia, hypertension, and fatigue. Anlotinib demonstrated promising efficacy and was well tolerated with controlled toxicity in patients with NSCLC.

Primary Clear Cell Sarcoma of the Ileum: A Case Report With Next-Generation Sequencing Analysis

As the concept of clear cell sarcoma-like tumor or malignant gastrointestinal neuroectodermal tumor (CCS-LT/MGNET) has been widely accepted, primary CCS of the gastrointestinal tract (CCS-GI) is becoming a rare entity. In this article, we describe a case of primary CCS-GI that occurred in the ileum of a 65-year-old male to further illustrate its rare occurrence. Similar to CCS of soft tissue (CCS-ST), the tumor was composed of spindled to epithelioid cells displaying fascicular, nested, or pseudopapillary arrangement. The tumor cells had large round to ovoid nuclei with vesicular chromatin and prominent nucleoli, containing eosinophilic to pale cytoplasm. In contrast to CCS-LT/MGNET, immunohistochemical study also showed variable positivity of HMB45, melan A, and MiTF besides the strong and diffuse staining of S100 protein and SOX10. Fluorescence in situ hybridization (FISH) using fusion probes identified EWSR1 and ATF1 genes rearrangement. Next-generation sequencing (NGS) analysis further revealed EWSR1 exons9/8-ATF1 exon4 and ATF1 exon3- EWSR1 exon11 fusion genes. CCS-GI and CCS-LT/MGNET possibly represent 2 related entities of the same spectrum, which differentiate along 2 different pathways.

Malignant gastrointestinal neuroectodermal tumor with BRAF mutation and a history of malignant melanoma: A case report

Malignant gastrointestinal neuroectodermal tumors (GNETs), also called clear-cell sarcoma-like tumors of the gastrointestinal tract, are rare and highly aggressive tumors originating in the gastrointestinal tract. These tumors are generally immunohistochemically positive for S-100 protein (S-100) and SRY-related HMG-box 10 (SOX10), and often contain EWSR1-ATF1 or EWSR1-CREB1. The histological features of GNETs overlap with those of clear-cell sarcoma of the tendons and aponeuroses. However, GNETs immunohistochemically lack melanocyte-specific markers and often demonstrate positivity for CD56, synaptophysin and neuron-specific enolase. The present case reports a woman with a history of desmoplastic malignant melanoma exhibiting a BRAF mutation, which later transformed into a GNET of the small intestine with both a BRAF mutation and two subtypes of EWSR1-ATF1 fusion genes. Tumor cells were revealed to be weakly immunoreactive or negative for S-100 and SOX10, lacked markers of melanocytic differentiation and were focally positive for CD56. Combination therapy with dabrafenib mesylate and trametinib dimethyl sulfoxide proved to be temporarily effective against this tumor. The present case is relatively unique as, to the best of our knowledge, there is no case of GNET with a history of melanoma. Furthermore, there is no report of GNET exhibiting both a BRAF mutation and an EWSR1-ATF1 fusion gene. Further accumulation of similar cases is necessary to elucidate the pathological significance of this GNET having a BRAF mutation.

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.

Malignant Gastrointestinal Neuroectodermal Tumors: Clinicopathological and Prognostic Features of 96 Patients

Purpose

Gastrointestinal neuroectodermal tumors (GNETs) are uncommon malignant tumors derived from ectodermal primitive neural cells.

Patients and Methods

We retrospectively analyzed 2 GNET cases at our hospital and the remaining 94 cases in the literature to determine clinicopathological prognostic factors.

Results

The patients had a mean age of 36 years and a median tumor size of 4.5 cm. A total of 67.0% of the tumors were located in the small intestine, and 76.4% of the patients presented recurrence or metastasis. There was a significant difference in sex and presence of osteoclast-like cells (P<0.01). Microscopically, most cells were round or short spindle-like in shape, with weak eosinophilic or clear cytoplasm. Neoplastic cells were always arranged in solid sheets, nests, and pseudoalveoli. Immunohistochemistry showed strong, diffuse S100 and SOX10 expression, with a complete absence of HMB45 and Melan-A expression. A total of 72.9% of the cases revealed genetic EWSR1 recombination, including our 2 cases. The median time to death and first metastasis was 61 months and 12 months, respectively. K-M analysis showed a great difference in survival according to lymph node invasion or distant metastasis (M+N), independent lymph node metastasis (N), lower histological grades (G2), and aggressive chemoradiotherapy (P=0.026, P=0.027, P=0.039 and P=0.037). However, independent T, independent M, and postoperative routine adjuvant therapy showed no statistical influence on overall survival or disease-free survival.

Conclusion

GNET is a new entity distinct in its clinical, morphological, immunochemical, and genetic features. Radical excision, close follow-up and adjuvant therapy may be effective for prolonged survival.

Recurrent uterine tumors resembling ovarian sex-cord tumors with the growth regulation by estrogen in breast cancer 1-nuclear receptor coactivator 2 fusion gene: a case report and literature review

BACKGROUND

Uterine tumors resembling ovarian sex-cord tumors (UTROSCTs) are rare mesenchymal neoplasms predominantly arising in perimenopausal and postmenopausal women. UTROSCTs with growth regulation by estrogen in breast cancer 1 (GREB1)-rearrangement or GREB1-rearranged uterine tumors are exceptionally rare, with only 12 previously reported cases. Here, we report a case of UTROSCT with the GREB1-nuclear receptor coactivator 2 (NCOA2) fusion gene.

CASE PRESENTATION

A 57-year-old woman presented with a 10.0 cm uterine mass. The tumor was composed of short spindle or epithelioid cells, arranged in diffused sheets, nested, and trabecular/cordlike. The tumor harbored the GREB1-NCOA2 fusion gene, as confirmed by RNA sequencing. The tumor recurred in the pelvis at 30 months after the initial diagnosis. We also compared the clinical and pathologic features of this case with those of the 12 previously published uterine GREB1-rearranged tumors. Of the combined 13 cases (present case and 12 previous cases), the mean age of patients was 64.8 years (range, 51-74 years). Of the nine reported cases of GREB1-rearranged tumor with follow up, four cases recurred or metastasized (44.4%). Microscopically, most tumors (10/12, 83.3%) showed infiltrative growth, and two were well demarcated. Mitotic figures ranged from 0 to 14 per 10 high-power fields (2 mm²; mean: 3.6). Lymphovascular invasion and necrosis were each present in two cases (2/12, 16.7% and 2/7, 28.6%, respectively).

CONCLUSIONS

This case provided further evidence that UTROSCTs with GREB1-rearrangement may have a high risk of recurrence/metastasis. Further studies are necessary to clarify the clinical features of this type of tumor, particularly the prognosis, potential treatment, and range of possible molecular events.

Malignant Gastrointestinal Neuroectodermal Tumor (GNET) with Prolonged Disease-Free Survival after Platinum-Based Chemotherapy

Malignant gastrointestinal neuroectodermal tumor (GNET) is a rare disease with a handful of cases described in literature. GNET has only become a well-known/widely accepted entity in the recent years, but it is still not listed in the database of rare diseases. Due to the rarity of disease, there are no guidelines on standard therapeutic approaches in the adjuvant or metastatic setting. Here, we describe a unique case of GNET with a 7-year disease-free survival following adjuvant cisplatin and etoposide chemotherapy. This is the longest disease-free survival that has ever been described in literature and may support using this combination in a larger cohort of patients in the context of a global clinical trial. We will also review the histopathologic features of GNET and potential therapeutic options in the metastatic setting.

Gastric Ewing Sarcoma identified on a Meckel's scan

Ewing Sarcoma is a malignant small round blue cell tumor most commonly found in bones and soft tissues of the axial skeleton and extremities. The Ewing family of tumors, including peripheral neuroectodermal tumor, represent the second most common malignancy in the pediatric population and second most common primary bone tumor after osteosarcoma. In a majority of Ewing Sarcoma cases, there is a translocation between chromosomes 11 and 22. Extraskeletal Ewing Sarcoma of the stomach is exceptionally rare, with only a handful of case reports. Here we report a case of primary Ewing Sarcoma of the stomach found initially as a filling defect in the stomach on technetium-99m pertechnetate scintigraphy to evaluate for gastrointestinal bleeding.