Malignant Gastrointestinal Neuroectodermal Tumor in the Right Atrium: The First Case Report Presenting with an Extra-Gastrointestinal Mass

Abstract Background: Malignant gastrointestinal neuroectodermal tumor is an extremely rare soft tissue sarcoma which was firstly described in 2003 but until recently it had been designated as a definite new entity. According to the previous literatures, Malignant gastrointestinal neuroectodermal tumor was almost exclusively occurred in gastrointestinal tract.Case presentation: A 62-year-old male showed a mass in right atrium and the occupying mass was founded on the right ventricular diaphragm and involved the right atrium along the coronary sinus during the operation. Microscopically, the tumor characterized by the solid sheet and pseudopapillary focally architectures, and was composed of small to medium cells with round or oval nuclei, variable amount of eosinophilic or clear, and frequent mitotic figures. 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 involving fusion of EWSR1 exon 8 with ATF1 exon 4 by whole transcriptome sequence analysis.Conclusions: This is the first case report of extra-gastrointestinal Malignant gastrointestinal neuroectodermal tumor that occurring in the right atrium，which remind of the new prospect of the tumor location.