Malignant Gastrointestinal Neuroectodermal Tumor Research Articles

Extra-abdominal and intra-abdominal FET::CREM fusion mesenchymal neoplasms: comparative clinicopathological study of 9 new cases further supporting a distinct potentially aggressive sarcoma and report of novel sites.

With the wide use of RNA sequencing technologies, the family of FET::CREB fusion mesenchymal neoplasms has expanded rapidly to include potentially aggressive neoplasms, not fitting any well established WHO entity. Recently, a group of intra-abdominal FET(EWSR1/FUS)::CREB(CREM/ATF1) fused unclassified neoplasms has been reported followed by recent recognition of an analogous extra-abdominal category of unclassified neoplasms carrying EWSR1::ATF1 fusions. We describe 9 additional tumors (5 extra-abdominal and 4 abdominal) carrying an EWSR1::CREM (n = 8) and FUS::CREM (n = 1) fusion. Patients were 7 females and 2 males aged 10 to 75years (median, 34). Extra-abdominal tumors originated in the head and neck (2 sinonasal, 1 orbital) and soft tissues (1 gluteal, 1 inguinal). Abdominal tumors involved stomach (2), mesentery (1), and kidney (1). Tumor size ranged from 3.5 to 11cm (median, 6). Treatment was radical surgery with (5) or without (2) neo/adjuvant radio/chemotherapy. Extended follow-up of 5 patients (21-52months; median, 24) showed an aggressive course in two (40%); one died of disseminated metastases 52months after several intensified chemotherapy regimens, and one was alive with progressive abdominal disease at 21months. The immunophenotype of the two subcohorts was significantly overlapping with variable expression of EMA (7 of 8), keratin AE1/AE3 (5 of 9), CD99 (4 of 7), MUC4 (2 of 8), ALK (3 of 8), synaptophysin (3 of 9), chromogranin (1 of 8), CD34 (3 of 6), CD30 (1 of 6), PAX8 (1 of 7), and inhibin (1 of 7), but no reactivity with desmin (0 of 8), S100 (0 of 8), and SOX10 (0 of 8). This series further solidifies the notion that FET::CREB fusions are not limited to the triad of angiomatoid fibrous histiocytoma, clear cell sarcoma, and malignant gastrointestinal neuroectodermal tumor, but characterize an emerging family of potentially aggressive neoplasms occurring at both intra- and extra-abdominal sites. These tumors underscore the promiscuity of the FET::CREB fusions and highlight the pivotal role of phenotype-oriented classification of these neoplasms that share the same genotype, still featuring significant biological and behavioral distinctness.

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 20-56years. All primary tumors were extra-abdominal and deep-seated (chest wall, mediastinum, deltoid, and parapharyngeal soft tissue). Their size ranged 4.4-7.5cm (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 (8-21months), 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.

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.

Malignant Gastrointestinal Neuroectodermal Tumor: A Case Report and Literary Review for a Rare Differential Diagnosis

Malignant gastrointestinal neuroectodermal tumor (GNET) is an infrequent soft-tissue sarcoma, formerly referred to as clear-cell sarcoma-like gastrointestinal tumor (CCSLGT) and frequently reported in the literature as clear-cell sarcoma of the gastrointestinal tract (CCS-GI); it is characterized by an absence of melanocytic differentiation and the presence of nontumoral osteoclast-like giant cells (OLGCs). The current study reports a case of a 79 year old woman admitted to the emergency department (ED) with symptoms of constipation and intestinal obstruction; a mass was found within the ileal wall necessitating of surgical approach. Immunohistochemically, tumor cells surprisingly had the hallmark of GNETs. Unfamiliarity with tumors with the features of GNETs can easily lead to a misdiagnosis by surgical pathologist. Therefore, comprehensive evaluation, including morphology and additional studies, is required for an appropriated diagnosis. Furthermore, without a high index of suspicion, there is actually no consensus on staging or treatment.

Malignant gastrointestinal neuroectodermal tumor

Malignant gastrointestinal neuroectodermal tumor (GNET) is a rare, aggressive, highly malignant mesenchymal tumor of the gastrointestinal tract. It commonly arises within the gastrointestinal tract, mostly involving the small intestine. The molecular features of GNET include chromosomal translocations t(12;22)(q13;q12) and t(2;22)(q34;q12) resulting in EWSR1–ATF1 and EWSR1–CREB1 gene fusions, respectively. Only a few cases of GNET in children and adolescents have been described in the international literature. Here, we report a case of metastatic GNET in a 6-year-old boy. The patient's parents gave their consent to the use of their child's data, including photographs, for research purposes and in publications. The diagnosis was confirmed histologically and by high-throughput RNA exome sequencing which revealed the typical EWSR1–ATF1 fusion transcript. In this article, we give the details of the patient's treatment that included intensive chemotherapy and the administration of the c-Met/ ALK inhibitor crizotinib with a transient antitumor effect. We also provide a literature review describing the clinical features and pathogenesis of GNET, its differential diagnosis and treatment approaches.

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

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.

Malignant gastrointestinal neuroectodermal tumor in head and neck: two challenging cases with diverse morphology and different considerations for differential diagnosis.

Malignant gastrointestinal neuroectodermal tumor (MGNET) is a sarcoma typically involving the gastrointestinal tract with neuroectodermal differentiation and EWSR1-ATF1/CREB1 fusions. Recently, rare MGNET cases were reported in extragastrointestinal sites. We identified 2 cases of MGNET arising in unprecedented laryngeal and intracranial locations, respectively. Both cases showed spindle and epithelioid tumor cells with amphophilic to clear cytoplasm and occasionally prominent nucleoli, arranged in solid, fascicular, and pseudoalveolar patterns. Case 1 exhibited moderate to marked nuclear atypia and focal intraepithelial component. In contrast, case 2 comprised predominantly low-grade epithelioid cells with extensive pseudopapillary structures. Both tumors showed an S100/SOX10-positive and HMB45/melan-A-negative immunoprofile as well as EWSR1-ATF1 fusion. A chief obstacle in diagnosing case 1 was the histologic and immunophenotypic resemblance to melanoma. The striking pseudopapillary architecture and the intracranial location of case 2 rendered differential diagnoses including meningioma and ependymoma. With the peculiar locations and morphology, these cases posed great diagnostic challenge.

Mesenchymal tumors and tumor-like lesions of the gastrointestinal tract: an overview

Mesenchymal tumors and tumor-like lesions of the gastrointestinal (GI) tract are uncommon. They vary from reactive tumefactive lesions and benign neoplasms to highly aggressive sarcomas. Among them, GI stromal tumors (GISTs) are most common, followed, with less frequency, by smooth muscle and neurogenic tumors. The major challenge resides in correctly identifying GISTs and providing acomprehensive report (including risk assessment and genotyping) that represents the basis for an optimized surgical-oncological treatment and/or adjuvant therapy. On the other hand, the challenge of benign lesions is to find agood name (well understandable and reproducible diagnostic term) that helps avoid diagnostic ambiguity and prognostic uncertainty so that overprognostication and overtreatment can be prevented. Moreover, several recently described genetically defined benign and malignant entities need be correctly diagnosed due to their special "targeted" therapeutic options and to further characterize their clinicopathological and biological properties in the future. These recent entities include aggressive epithelioid inflammatory myofibroblastic sarcoma (ALK-RANBP2-driven), malignant gastrointestinal neuroectodermal tumor (EWSR1-ATF1/CREB-related), NTRK-rearranged neoplasms, and, most recently, colorectal NUTM1-rearranged sarcomas. This review highlights the major clinicopathological features of gastrointestinal mesenchymal lesions in light of recent developments.

Malignant Gastrointestinal Neuroectodermal Tumor: a case report and a review of the literature

Abstract Introduction/Objective Malignant gastrointestinal neuroectodermal tumor (GNET) is a rare soft tissue tumor arising in the wall of the gastrointestinal tract. The GNET was first described as an osteoclast rich tumor of the gastrointestinal tract with features resembling clear cell sarcoma, with only few cases reported in the literature. Methods/Case Report We report a case of a 71-year-old man with a past medical history of hypertension, hyperlipidemia, and benign prostatic hyperplasia presented with complaints of dyspnea, dizziness, fatigue, black stools, and a recent syncopal episode. Laboratory testing revealed anemia (HB 5.4 g/dL). Esophagogastroduodenoscopy demonstrated a submucosal gastric mass. An abdominal CT scan confirmed a 7.8 cm mass along the gastric cardia and fundus. Results (if a Case Study enter NA) Biopsy rendered a gastrointestinal neuroectodermal tumor (GNET). Microscopically, the tumor cells were spindle with eosinophilic cytoplasm and arranged in fascicules. They were positive for CD56, CD99, and Fli-1, synaptophysin, and negative for chromogranin, TTF-1, SMA, desmin, CD34, EMA, pan-cytokeratin, and lymphoid markers. Two months later, further imaging confirmed metastasis to the liver and spleen. GNETs typically arise within the muscularis propria of the gastrointestinal tract and often extend into the submucosa and subserosa. Conclusion The most important differential of GNET is the clear cell sarcoma of the gastrointestinal tract (CCS-GI). Both share similar morphological as well as molecular features and show S100 positivity; however, the lack of melanocytic differentiation in GNET distinguishes it from CCS-GI. Both typically show rearrangements of the EWSR1 gene, with t(12;22) (q13;q12) EWSR1-ATF1 or t(2;22)(q34;q12) EWSR1-CREB1 fusions. Pathologists should be aware of GNET diagnostic entity due to its aggressive behavior and high rate of recurrence and mortality even after complete resection.

Malignant gastrointestinal neuroectodermal tumor: Cytologic, histologic, immunohistochemical, and molecular pitfalls

Malignant gastrointestinal neuroectodermal tumor (GNET) is a rare malignant primary gastrointestinal mesenchymal tumor which can be diagnosed via fine-needle aspiration (FNA) cytology. In the context of FNA, the diagnosis requires a cell block and the use of significant resources including immunohistochemical stains and molecular testing. The differential diagnosis of GNET includes clear cell sarcoma (CCS), gastrointestinal stromal tumor (GIST), gastric schwannoma, metastatic melanoma, malignant perivascular epithelioid cell tumor (PEComa) and granular cell tumor, among others. Here we describe a case which was initially diagnosed as malignant granular cell tumor by FNA which was later revised to GNET following the finding of an EWSR1-ATF1 fusion gene rearrangement.

Malignant gastrointestinal neuroectodermal tumor: clinicopathological analyses of four cases

Objective: To investigate the clinicopathological features, diagnosis, differential diagnosis, and molecular alterations of malignant gastrointestinal neuroectodermal tumor (MGNET). Methods: Four cases of MGNET were collected at Fujian Provincial Hospital, from July 2013 to January 2019. H&E and immunohistochemical staining were retrospectively evaluated, together with genetic mutation analysis of EWSR1. The relevant literature was systematically reviewed. Results: There were two male and two female patients, with an age range of 34-81 (median 57) years. Tumor sizes ranged from 5-9 (median 6.8) cm. Microscopy showed diffuse and flaky growth of tumor cells, some of which were small and round. The tumor cells were arranged in solid, flaky, nested or pseudoadenoid patterns. The tumor cells were epithelioid, oval, short spindled, or small, with round or oval nuclei. The cytoplasm was eosinophilic or clear. Osteoclast-like multinucleated giant cells were scattered focally. Mitosis was about (2-10)/10 HPF. Immunohistochemically, the tumor cells were positive for S-100 protein (4/4), SOX10 (4/4), Syn (2/4), INI1 (4/4), H3K27Me3 (4/4) and vimentin (4/4). Ki-67 index was 15%-90%. Gene mutation detection confirmed EWSR1 mutation in all four cases, and C-KIT/PDGFRα genes were not mutated in two cases. Conclusions: MGNET is a rare high grade malignant soft tissue tumor. The diagnosis is based on clinicopathological, immunophenotypic, and molecular pathology features. The primary treatment for MGNET is complete surgical excision and chemotherapy; the prognosis is poor.

Malignant Gastrointestinal Neuroectodermal Tumor

A malignant gastrointestinal neuroectodermal tumor (GNET) is rare, and it is therefore yet to be completely understood. This study aimed to present the clinicopathologic features of GNET, including treatment information. We included 19 patients with GNET with a mean tumor size of 4.2 cm. The most common site of tumor origin was the small intestine (57.9%), followed by the stomach (15.8%), colon (10.5%), ileocecal junction (5.3%), lower esophagus (5.3%), and anal canal (5.3%). Microscopically, the tumors were composed of epithelioid cells with eosinophilic or clear cytoplasm arranged in nest, sheet-like, papillary, or pseudoalveolar patterns and/or spindle tumor cells with eosinophilic cytoplasm arranged in a fascicular pattern. Immunohistochemically, the tumor cells stained positively for S100 (19/19,100%), SOX10 (14/15, 93.3%), vimentin (17/17, 100%), synaptophysin (Syn) (7/17, 41.2%), CD56 (4/13, 30.8%), CD99 (1/5, 20%), and CD117 (1/15, 6.7%), and negatively for HMB45, Melan A, DOG1, CD34, AE1/AE3, CAM5.2, chromogranin A, smooth muscle actin, and desmin. In total, 14/15 (93.3%) cases showed split Ewing sarcoma breakpoint region 1 gene (EWSR1) signals consistent with a chromosomal translocation involving EWSR1. Within a mean follow-up of 29.7 months (range: 3 to 63 mo), 2/15 (13.3%) patients died of disease, 5 (33.3%) were alive with disease, and 8 (53.3%) had no evidence of disease. Two and 1 patients showed partial response to apatinib and anlotinib, respectively. In conclusion, GNET has distinctive morphologic, immunohistochemical, and molecular genetic features and should be distinguished from other gastrointestinal tract malignancies. Apatinib and anlotinib might be effective for the treatment of advanced GNET and could prolong patient survival.

Primary malignant gastrointestinal neuroectodermal tumor occurring in the ileum with intra-abdominal granulomatous nodules: A case report and review of the literature.

Malignant gastrointestinal neuroectodermal tumors (GNETs) are rare aggressive malignant neoplasms that exclusively occur within the wall of the gastrointestinal tract. The GNET was first described as an ‘osteoclast-rich tumor of the gastrointestinal tract with features resembling clear cell sarcoma (CCS) of soft parts’ in 2003. Although the GNET shares certain histological features with CCS, it is characterized by a lack of melanocytic differentiation and the presence of non-tumoral osteoclast-like giant cells (OLGCs). The present study reports a case of a GNET of the ileum with intra-abdominal granulomatous nodules, an uncommon accompanying finding, and summarizes the current literature. A 30-year-old woman presented with the symptoms of intestinal obstruction, and a mass was found within the ileum wall. Multiple grey-white nodules were found adhering to the omentum and serosa of the ileum. Histologically, the tumor was located in the muscularis propria and infiltrated the mucosa and the serosa. Tumor cells presented with oval or polygonal nuclei and prominent nucleoli, and were predominantly arranged in nested and pseudopapillary patterns, with the presence of cluster of differentiation (CD)68-positive, scattered OLGC. Immunohistochemically, it was determined that the tumor cells expressed Vimentin, CD56, S-100 and transcription factor SOX-10, while being negative for pan-cytokeratin, cytokeratin (CK)7, CK20, synaptophysin, chromogranin-A, CD117, anoctamin-1, CD34, human melanoma black-45, Melan-A, smooth muscle actin, CD3 and CD20 expression. Ewing sarcoma breakpoint region 1 gene rearrangement was identified by fluorescence in situ hybridization analysis. Ultrastructurally, no typical melanosomes were identified. In addition, the intra-abdominal grey-white nodules were microscopically identified as chronic granulomatous inflammation. The patient received four cycles of adjuvant chemotherapy following routine tumor resection. Due to its rarity and histological similarity with other neoplasms, unfamiliarity with the features of GNETs by surgical pathologists can easily lead to a misdiagnosis. Therefore, comprehensive assessments, including morphology and ancillary studies, are required for an accurate diagnosis of GNET.

Malignant gastrointestinal neuroectodermal tumor: a case report and review of the literature

BackgroundMalignant gastrointestinal neuroectodermal tumor (GNET) is an extremely rare entity that was first described by Zambrano et al. in 2003 as “Clear cell sarcoma-like tumor of the gastrointestinal tract”. It shares some of the histological features of clear cell sarcoma (CCS) but lacks the immunohistochemical reactivity for melanocytic markers. We report a case of GNET that was initially misdiagnosed as gastrointestinal stromal tumor (GIST). Recognizing this entity is important to avoid misdiagnosis.Case presentationA case of an 18-year-old male presented with a small intestinal tumor. Histologically it was characterized by polygonal cells arranged in pseudoalveolar pattern and situated in the muscularis propria. Scattered osteoclast-like multinucleated giant cells were also noted. The neoplastic cells were positive for S-100 protein and negative for HMB-45, Melan A, smooth muscle actin, desmin and CD117. EWSR1 gene rearrangement was detected by fluorescence in situ hybridization (FISH) analysis. The patient returned with recurrence after 36 months’ management by surgical resection and died one year later.ConclusionsGNET can be mistaken histologically for other non-epithelial gastrointestinal tumors. Awareness of its existence and diagnostic criteria by the pathologist is necessary to avoid misdiagnosis, particularly as GIST, CCS or malignant peripheral nerve sheath tumor (MPNST).

Gastrointestinal Neuroectodermal Tumor: a Diagnostic Dilemma.

Malignant gastrointestinal neuroectodermal tumor (GNET), a rare soft tissue sarcoma, is a recently described distinct clinicopathological entity. With only a few cases reported in literature till date, there is limited knowledge about the behavior as well as diagnosis of this tumor. GNET mimics several other tumors and hence presents as a diagnostic challenge to clinicians and pathologists alike. We report a case of gastrointestinal neuroectodermal tumors with liver metastasis.

Esophageal subepithelial lesion diagnosed as malignant gastrointestinal neuroectodermal tumor

A 21-year-old male visited our hospital with a complaint of aggravating dysphagia and odynophagia for a few days. Esophagogastroduodenoscopy showed huge bulging mucosa with an intact surface causing luminal narrowing at 35 cm from the incisor teeth. Endoscopic ultrasonography showed an about 35 mm sized irregular margined in-homogenous hypoechoic lesion with an obscure layer of origin. Endoscopic ultrasonography fine needle aspiration revealed spindle cell proliferation without immunoreactivity for CD117, SMA, and cytokeratin. The patient underwent excision of the subepithelial lesion at the distal esophagus. On pathologic examination of the specimen, the tumor was composed of short fascicles of oval to spindle cells with eosinophilic and clear cytoplasm and vesicular nuclei. The tumor cells were positive for S-100 and SOX10 and negative for CD117, SMA, HMB-45, melan-A, cytokeratin, and CD99. The split-apart signal was detected in EWSR1 on FISH, suggesting a malignant gastrointestinal neuroectodermal tumor. At the time of writing, the patient is on radiation therapy at the operated site of esophagus and doing well, with no recurrence for three months. Malignant gastrointestinal neuroectodermal tumor is a rare gastrointestinal tumor with features of clear cell sarcoma, without melanocytic differentiation, and shows a poor prognosis. This is the first reported case of malignant gastrointestinal neuroectodermal tumor arising as subepithelial lesion in the esophagus.

Malignant Extragastrointestinal Neuroectodermal Tumor Located at Right Cervical Region

Malignant Gastrointestinal Neuroectodermal Tumor (GNET) is a recently described rare malignant neoplasm, resembling “clear cell sarcoma of tendons and aponeuroses” morphologically, immunohistochemically and molecular pathologically. We will describe a case of soft tissue sarcoma located at right cervical region of a 9-year-old male patient, mimicking malignant GNET, which can be considered as extragastrointestinal counterpart of this tumor. These tumors have poor prognosis. This is unique, possibly the first case of a soft tissue sarcoma resembling GNET.

Malignant gastrointestinal neuroectodermal tumor: A case report and review of the literature.

Malignant gastrointestinal neuroectodermal tumor (GNET) is a rare soft tissue sarcoma, previously referred to as clear cell sarcoma-like gastrointestinal tumor (CCSLGT) and also commonly reported in the literature as clear cell sarcoma of the gastrointestinal tract (CCS-GI). The current study reports a case of GNET arising in the stomach of a 17-year-old male, who presented with symptoms of fatigue, anemia and low temperature. Examination with positron emission tomography-computed tomography revealed a soft tissue mass in the gastric antrum. Subsequently, radical distal gastric resection was performed, and the mass measured 6.0×4.0×3.5 cm3. Histopathological analysis revealed that the tumor cells were arranged in nests and focally formed fascicular, pseudopapillary, pseudoalveolar and rosette-like growth patterns. Osteoclast-like giant cells were also observed. Immunohistochemically, the tumor cells were positive for S-100 protein, vimentin and BCL-2, and negative for HMB45, Melan-A, CD117, CD34 and CD99. Additionally, the osteoclast-like giant cells were positive for CD68. Fluorescence in situ hybridization demonstrated EWSR1 gene rearrangement. After 10 months of follow-up, no evidence of recurrence or metastasis was observed. As GNET is currently classified differently and under various names in the literature, the information provided by this case study and review is predicted to be useful towards the accurate diagnosis, treatment and prognosis of this rare tumor type.

Malignant Gastrointestinal Neuroectodermal Tumor Showing Overlapped Immunophenotype With Synovial Sarcoma

Suárez-Vilela, Dimas MD; Izquierdo, Francisco M. MD; Tojo-Ramallo, Sergio MD; R. Riera-Velasco, Jose MD, PhD; Escobar-Stein, Juliana MD Author Information

Malignant Gastrointestinal Neuroectodermal Tumor

The clinical, histologic, immunophenotypic, ultrastructural, and molecular features of a distinctive gastrointestinal tumor are described. Sixteen patients, 8 women and 8 men aged 17 to 77 years (mean age, 42 y; 63% less than 40 y) presented with abdominal pain, intestinal obstruction, and an abdominal mass. Mean tumor size was 5.2 cm (range, 2.4 to 15.0 cm). The tumors arose in the small bowel (10), stomach (4), and colon (2) and were histologically characterized by a sheet-like or nested population of epithelioid or oval-to-spindle cells with small nucleoli and scattered mitoses. Five cases showed focal clearing of the cytoplasm. Scattered osteoclast-type multinucleated giant cells were present in 8 cases. The tumor cells were positive for S-100 protein, SOX10, and vimentin in 100% of cases, for CD56 in 70%, for synaptophysin in 56%, for NB84 in 50%, for NSE in 45%, and for neurofilament protein in 14% of cases. All cases tested were negative for specific melanocytic, gastrointestinal stromal tumors, epithelial, and myoid markers. Ultrastructural examination of 5 cases showed features of primitive neuroectodermal cells with clear secretory vesicles, dense-core granules, occasional gap junctions, and no evidence of melanogenesis. EWSR1 gene rearrangement was assessed by fluorescence in situ hybridization in 14 cases. Twelve cases (86%) showed split EWSR1 signal consistent with a chromosomal translocation involving EWSR1. One case showed extra intact signals, indicating that the nuclei possessed either extra copies of the EWSR1 gene or chromosome 22 polysomy. Only 1 case showed no involvement of the EWSR1 gene. Six cases demonstrated rearrangement of the partner fusion gene ATF1 (46%), and 3 showed rearrangement of CREB1 (23%); 2 cases lacked rearrangement of either partner gene. Clinical follow-up was available in 12 patients and ranged from 1.5 to 106 months. Six patients died of their tumors (mean survival, 32 mo; 83% less than 24 mo). At last follow-up, 4 patients were alive with regional, lymph node, and liver metastases, and 2 patients were alive with no evidence of disease. The tumor described here is an aggressive form of neuroectodermal tumor that should be separated from other primitive epithelioid and spindle cell tumors of the gastrointestinal tract. The distinctive ultrastructural features and absence of melanocytic differentiation serve to separate them from soft tissue clear cell sarcomas involving the gastrointestinal tract. The designation "malignant gastrointestinal neuroectodermal tumor" is proposed for this tumor type.