Abstract：
Retroperitoneal Ewing sarcomas (RES) are very rare and mostly described in case reports. The purpose of this study was to retrospectively analyze the clinicopathology, molecular characteristics, biological behavior, and therapeutic information of 13 cases of primary RES with immunohistochemical staining, fluorescence in situ hybridization, RT-PCR and NGS sequencing detection techniques. The thirteen patients included eight males and five females with a mean age of 34 years. Morphologically, the tumors were comprised of small round or epithelial-like cells with vacuolated cytoplasm (6/13,46 %) arranged in diffuse, nested (8/13,62 %) and perivascular (7/13,54 %) patterns. Unusual morphologic patterns, such as meningioma-like swirling structures and sieve-like structures were relatively novel findings. Immunohistochemical studies showed CD99 (12/13; 92 %), CD56 (11/13; 85 %), NKX2.2 (9/13; 69 %), PAX7 (10/11;91 %) and CD117(6/9;67 %) to be positive.12 cases (92 %) demonstrated EWSR1 rearrangement and 3 cases displayed EWSR1::FLI1 fusion by FISH. ERCC4 splice-site variant, a novel pathogenic variant, was discovered for the first time via RNA sequencing. With a median follow-up duration of 14 months (6 to 79 months), 8/13 (62 %) patients died, while 5/13(38 %) survived. Three cases recurred, and five patients developed metastasis to the liver (2 cases), lung (2 cases) and bone (1 case). RES is an aggressive, high-grade tumor, prone to multiple recurrences and metastases, with distinctive morphologic, immunohistochemical, and molecular genetic features. ERCC4 splicing mutation, which is a novel pathogenic variant discovered for the first time, with possible significance for understanding the disease, as well as the development of targeted drugs.
摘要：
腹膜后尤因肉瘤（RES）非常罕见，主要在病例报告中描述。这项研究的目的是回顾性分析临床病理，分子特征，生物学行为,免疫组织化学染色13例原发性RES的治疗信息，荧光原位杂交,RT-PCR和NGS测序检测技巧。13名患者包括8名男性和5名女性,平均年龄为34岁。形态学上,肿瘤由小的圆形或上皮样细胞组成，细胞质呈空泡状（6/13,46％），呈弥漫性排列，嵌套（8/13,62％）和血管周围（7/13,54％）模式。不寻常的形态模式，如脑膜瘤样漩涡结构和筛状结构是相对新颖的发现。免疫组织化学研究显示CD99(12/13;92%)，CD56（11/13；85%），NKX2.2（9/13；69%），PAX7(10/11；91%)和CD117(6/9；67%)阳性。12例(92%)显示EWSR1重排，3例显示EWSR1::FLI1融合。ERCC4剪接位点变异体,一种新的致病变种,首次通过RNA测序发现。中位随访时间为14个月（6至79个月），8/13（62%）患者死亡，而5/13（38％）存活。三例复发，5例发生肝转移（2例），肺(2例)和骨(1例)。RES是一个侵略性的，高级别肿瘤，容易多次复发和转移，具有独特的形态，免疫组织化学，和分子遗传特征。ERCC4剪接突变,这是首次发现的一种新的致病变异，对了解这种疾病可能有意义，以及靶向药物的开发。
