胃肠道恶性神经外胚层肿瘤临床病理观察

Malignant gastrointestinal neuroectodermal tumor: report of a case with clinicopathological and molecular study

目的探讨胃肠道恶性神经外胚层肿瘤(MGNET)的临床病理特点、免疫表型、分子遗传学改变、诊断与鉴别诊断要点。方法报道1例罕见的胃肠道恶性神经外胚层肿瘤,复习相关文献,分析其组织学形态及免疫组化标记结果,并采用荧光原位杂交方法检测EWSRl基因融合情况。结果肿瘤位于小肠,病变在黏膜下,周界不清,明显浸润性生长。肿瘤组织主要呈弥漫片状、巢状、假乳头状排列;瘤细胞呈上皮样、卵圆形、梭形,胞质嗜酸或透明,核圆形或卵圆形,呈空泡状,核仁不明显,偶见小核仁,核分裂象可见。免疫组化:肿瘤细胞一致性SOX10、S-100和vimentin(+),部分瘤细胞CD56、Syn和NSE(+),Ki-67增殖指数30%。荧光原位杂交检测显示EWSRl基因重排。结论胃肠道恶性神经外胚层肿瘤罕见,具有高度侵袭性,预后差。对该肿瘤确诊主要依靠组织学形态和免疫组化,且需要与其他肿瘤如单相型滑膜肉瘤、胃肠间质瘤以及血管周上皮样细胞肿瘤等鉴别。EWSRl融合基因检测有助于确诊及鉴别诊断。

Objective To investigate the clinicopathological features,immunophenotype,molecular alteration and differential diagnosis of malignant gastrointestinal neuroectodermal tumor（ MGNET）. Methods A case of rare malignant gastrointestinal neuroectodermal tumor was analyzed with histological observation and immunohistochemical examination,and the related literatures were reviewed. The status of EWSRl fusion gene was also assessed by fluorescence in situ hybridization. Results The neoplasm was located in the small bowel. Histologically,the poor-circumscribed lesion located predominantly in the submucosa with a significant infiltrative growth. The tumor mostly arranged in diffuse sheets,nests and pseudopapillary growth patterns. The tumor cells displayed a predominantly epithelioid or oval-to-spindle appearance and contained round or oval nuclei surrounded by variable amounts of eosinophilic cytoplasm. The nuclei showed vesicular chromatin with generally indistinct to small nucleoli,occasional prominent nucleoli and variable mitotic activity that ranged from 0 to 20 mitoses per 10 HPF. Immunohistochemically,the tumor cells were strongly positive for SOX10,S-100 and vimentin,and partly positive for CD56,Syn and NSE. The Ki67 proliferating index was about 30%.The split-apart EWSR1 signals were observed in the neoplastic cells by FISH analysis. Conclusions MGNET is a rare tumor with high aggressive and poor prognosis. The definite diagnosis for it mainly depends on the histology,immunophenotype,at the same time,needs to be differentiated from other tumors such as monophase synovial sarcoma,gastrointestinal stromal tumor and perivascular epithelioid cell tumor. The rearrangement analysis of EWSRl gene is helpful for pathologic diagnosis.