Desmoplastic small round cell tumor (DSRCT) is an aggressive pediatric round cell sarcoma containing a characteristic EWSR1-WT1 gene fusion. In the absence of genetic data, distinguishing DSRCT from other small round cell tumors of childhood can be problematic due to overlapping histologic and immunohistochemical features. We studied the utility of immunohistochemistry with antibodies targeting both the amino-terminal and carboxy-terminal regions of the Wilms tumor-1 (WT1) protein in differentiating these groups of tumors. The study cohort included 33 cases of genetically confirmed pediatric round cell tumors (10 DSRCTs, 12 Wilms tumors, 10 Ewing sarcomas, and 1 CIC-rearranged sarcoma). Immunoreactivities and immunolocalization of both the WT1 amino-terminus and carboxy-terminus were scored and documented. All DSRCTs displayed selective reactivity for only the WT1 carboxy-terminus (10/10), while dual immunoreactivity for both the WT1 carboxy-terminus (12/12) and amino-terminus antibodies (12/12) were characteristic of Wilms tumors. CIC-rearranged sarcoma showed variable WT1 nuclear immunopositivity (1/1, 1/1) and Ewing sarcomas were consistently WT1-negative for both the WT1 amino-terminus (0/10) and carboxy-terminus (0/10). Dual WT1 amino-terminus and carboxy-terminus immunohistochemistry remains a helpful diagnostic tool in discriminating intraabdominal small round cell tumors, which serves as an adjunct to the genetic information in preventing misdiagnosis.

促纤维增生性小圆细胞瘤 (DSRCT) 是一种侵袭性小儿圆形细胞肉瘤，含有特征性的EWSR1-WT1基因融合。在缺乏遗传数据的情况下，由于组织学和免疫组织化学特征重叠，将 DSRCT 与其他儿童小圆形细胞肿瘤区分开来可能存在问题。我们研究了免疫组织化学与靶向 Wilms 肿瘤 1 (WT1) 蛋白的氨基末端和羧基末端区域的抗体在区分这些肿瘤组中的效用。研究队列包括 33 例经基因证实的儿科圆形细胞肿瘤（10 例 DSRCT、12 例 Wilms 肿瘤、10 例尤文肉瘤和 1 例CIC-重排肉瘤）。对 WT1 氨基末端和羧基末端的免疫反应性和免疫定位进行评分和记录。所有 DSRCT 仅对 WT1 羧基末端 (10/10) 显示选择性反应性，而 WT1 羧基末端 (12/12) 和氨基末端抗体 (12/12) 的双重免疫反应性是 Wilms 肿瘤的特征。CIC-重排肉瘤显示出可变的 WT1 核免疫阳性 (1/1, 1/1)，尤文肉瘤在 WT1 氨基末端 (0/10) 和羧基末端 (0/10) 中始终呈 WT1 阴性。双 WT1 氨基末端和羧基末端免疫组织化学仍然是鉴别腹内小圆形细胞肿瘤的有用诊断工具，可作为遗传信息的辅助手段，以防止误诊。