[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.目的： 探讨胃肠道恶性神经外胚层肿瘤（malignant gastrointestinal neuroectodermal tumor，MGNET）的临床病理及分子病理学特征，并分析其预后。 方法： 收集2013年7月至2019年1月福建省立医院诊断的4例MGNET，对4例进行HE染色、免疫组织化学染色及分子病理学研究，复习文献并综合分析。 结果： 男女各2例，年龄34~81岁（平均年龄57岁），肿块最大径5~9 cm（平均6.8 cm）。病理组织学上表现相似，瘤细胞排列成实性、片状、巢状或假腺样，部分呈小圆形细胞样；瘤细胞上皮样、卵圆形或短梭形，可见核仁，部分呈小细胞样，胞质嗜酸性或透明样，核分裂象（2~10）/10 HPF，可见散在分布破骨样多核巨细胞。免疫表型：瘤细胞呈S-100蛋白（4/4）、SOX10（4/4）、突触素（2/4）、INI1（4/4）、H3K27Me3（4/4）、波形蛋白（4/4）阳性。Ki-67阳性指数热点区域15%~90%。4例均检测到EWSR1基因分离信号，2例未见C-KIT、PDGFRα基因突变。 结论： MGNET属于胃肠道罕见恶性软组织肿瘤，诊断需结合临床病理、免疫表型及EWSR1基因检测。治疗以手术切除和化疗为主，预后较差。.