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

Retroperitoneal malignant extra-gastrointestinal neuroectodermal tumor with EWSR1::CREM fusion and IL-6-related systemic inflammatory symptoms: a case report

Malignant gastrointestinal neuroectodermal tumors (GNETs) are mesenchymal tumors that typically arise in the digestive tract and harbor EWSR1::ATF1 or EWSR1::CREB1 fusions. We report a case of primary retroperitoneal GNET in a 38-year-old woman who presented with a month-long fever with increased serum IL-6 level. A right retroperitoneal mass of 7 cm consisting of diffuse sheets of small cells with a high nuclear-to-cytoplasmic ratio and scattered osteoclast-like multinucleated giant cells was confirmed apart from the digestive tract. Peripheral lymphoid cuff and focal pseudoangiomatous spaces were present, reminiscent of angiomatoid fibrous histiocytoma. The tumor cells were positive for S100 protein and SOX10 and negative for melanocytic markers. Fluorescent in situ hybridization revealed EWSR1 and CREM gene rearrangements, consistent with EWSR1::CREM fusion, which has never been reported in GNET. The patient lives with recurrent lesions for 8 months. This case was associated with several unusual features and contributes to the evolving GNET concept.

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.