Abstract：
BACKGROUND: Malignant 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.
METHODS: A 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.
CONCLUSIONS: GNET 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).
METHODS: A 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.
CONCLUSIONS: GNET 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).
摘要：
背景：恶性胃肠道神经外胚层肿瘤（GNET）是Zambrano等人首次描述的一种极为罕见的实体。2003年被称为“胃肠道透明细胞肉瘤样肿瘤”。它具有透明细胞肉瘤（CCS）的一些组织学特征，但缺乏对黑素细胞标记的免疫组织化学反应性。我们报告了一例GNET，最初被误诊为胃肠道间质瘤（GIST）。认识到这一实体对于避免误诊是重要的。
方法：1例18岁男性表现为小肠肿瘤。从组织学上讲，它的特征是以假肺泡形式排列并位于固有肌层中的多边形细胞。还注意到分散的破骨细胞样多核巨细胞。肿瘤细胞S-100蛋白阳性，HMB-45、MelanA阴性，平滑肌肌动蛋白，desmin和CD117。通过荧光原位杂交(FISH)分析检测EWSR1基因重排。通过手术切除治疗36个月后，患者复发，并在一年后死亡。
结论：GNET可在组织学上误认为其他非上皮性胃肠道肿瘤。病理学家必须意识到其存在和诊断标准，以避免误诊。特别是作为GIST，CCS或恶性外周神经鞘瘤(MPNST)。
方法：1例18岁男性表现为小肠肿瘤。从组织学上讲，它的特征是以假肺泡形式排列并位于固有肌层中的多边形细胞。还注意到分散的破骨细胞样多核巨细胞。肿瘤细胞S-100蛋白阳性，HMB-45、MelanA阴性，平滑肌肌动蛋白，desmin和CD117。通过荧光原位杂交(FISH)分析检测EWSR1基因重排。通过手术切除治疗36个月后，患者复发，并在一年后死亡。
结论：GNET可在组织学上误认为其他非上皮性胃肠道肿瘤。病理学家必须意识到其存在和诊断标准，以避免误诊。特别是作为GIST，CCS或恶性外周神经鞘瘤(MPNST)。
