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Abstract：
Malignant gastrointestinal neuroectodermal tumor (MGNET) is a very rare, aggressive malignant neoplasm that may occur in any location in the gastrointestinal tract. Malignant gastrointestinal neuroectodermal tumors typically consist of sheet-like to pseudopapillary proliferation of primitive-appearing epithelioid cells with a moderate amount of lightly eosinophilic cytoplasm, round nuclei and small nucleoli, often in association with osteoclast-like giant cells. By immunohistochemistry, these tumors show expression of S100 protein and SOX10, in the absence of expression of more specific melanocytic markers (eg, HMB45, Melan A). Genetically, malignant gastrointestinal neuroectodermal tumors are characterized by rearrangements of the EWSR1 or FUS genes with CREB1 or ATF1. We report a case of gastric malignant gastrointestinal neuroectodermal tumor occurring in a 46-year-old woman and showing striking oncocytic cytoplasmic change, a previously undescribed potential diagnostic pitfall. An initial needle biopsy showed large, eosinophilic cells with S100 protein and SOX10 expression and lacking expression of KIT, DOG1, Melan A, keratin, chromogranin, or smooth muscle actin, and was interpreted as representing a granular cell tumor. The subsequent excision specimen showed similar-appearing areas, but also contained small more primitive-appearing areas, lacking oncocytic change and having high nuclear grade and brisk mitotic activity. This resection specimen was initially diagnosed as a malignant granular cell tumor. However subsequent gene expression profiling studies showed an EWSR1-ATF1 fusion, confirmed with fluorescence in situ hybridization for EWSR1, and a final diagnosis of MGNET with oncocytic change was made. This case highlights a previously undescribed pitfall in the diagnosis of MGNET, oncocytic change, and suggests that MGNET should be included in the differential diagnosis for unusual oncocytic neoplasms of the gastrointestinal tract.
摘要：
恶性胃肠道神经外胚层肿瘤(MGNET)是一种非常罕见的肿瘤,可能发生在胃肠道任何位置的侵袭性恶性肿瘤。恶性胃肠道神经外胚层肿瘤通常由原始出现的上皮样细胞的片状至假乳头状增生组成，并带有适量的轻度嗜酸性细胞浆。圆形核和小核仁，通常与破骨细胞样巨细胞有关。通过免疫组织化学，这些肿瘤显示S100蛋白和SOX10的表达，在缺乏更特异性的黑素细胞标志物的表达（例如，HMB45，MelanA）。基因上,恶性胃肠道神经外胚层肿瘤的特征是EWSR1或FUS基因与CREB1或ATF1的重排。我们报告了一例发生在46岁女性中的胃恶性胃肠道神经外胚层肿瘤，并显示出惊人的嗜酸细胞细胞质改变，先前未描述的潜在诊断缺陷。最初的穿刺活检显示大，嗜酸性粒细胞具有S100蛋白和SOX10的表达和缺乏KIT的表达,DOG1,MelanA,角蛋白,嗜铬粒蛋白,或平滑肌肌动蛋白，被解释为代表颗粒细胞瘤。随后的切除标本显示出相似的出现区域，但也包含较小的更原始的区域，缺乏嗜酸细胞变化，核级高，有丝分裂活性快。该切除标本最初被诊断为恶性颗粒细胞瘤。然而，随后的基因表达谱分析研究显示EWSR1-ATF1融合，通过EWSR1的荧光原位杂交证实，并最终诊断为MGNET伴嗜酸细胞改变。此病例凸显了MGNET诊断中先前未描述的陷阱，嗜酸性细胞改变,并建议MGNET应包括在胃肠道异常嗜酸细胞肿瘤的鉴别诊断中。
