Department of Pathology, University of California, San Francisco, San Francisco, CA 94158.
Department of Pediatrics, Division of Hematology-Oncology, University of California, San Francisco, San Francisco, CA 94158.
Hum Pathol. 2018 Nov;81:281-290. doi: 10.1016/j.humpath.2018.03.020. Epub 2018 Apr 4.
Mesenchymal round cell tumors are a diverse group of neoplasms defined by primitive, often high-grade cytomorphology. The most common molecular alterations detected in these tumors are gene rearrangements involving EWSR1 to one of many fusion partners. Rare EWSR1-NFATC2 gene rearrangements, corresponding to a t(20;22) gene translocation, have been described in mesenchymal tumors with clear round cell morphology and a predilection for the skeleton. We present a case of a tumor harboring the EWSR1-NFATC2 gene fusion arising in the subcutaneous tissue of a young woman. The tumor exhibited corded and trabecular architecture of epithelioid cells within abundant myxoid and fibrous stroma. The cells showed strong immunoreactivity for NKX2.2, variable CD99, keratin, and epithelial membrane antigen, but were negative for S100 and myoepithelial markers. Importantly, similar to previously reported cases, the clinical course was more indolent than that of Ewing sarcoma. This case highlights the distinctive clinicopathological characteristics of EWSR1-NFATC2 gene fusion-associated neoplasms that distinguish them from Ewing sarcoma.
间叶性圆形细胞肿瘤是一组由原始、常为高级别细胞形态学定义的多种肿瘤。这些肿瘤中最常见的检测到的分子改变是涉及 EWSR1 的基因重排，涉及许多融合伙伴之一。在具有明确圆形细胞形态和骨骼偏好的间叶性肿瘤中，已经描述了罕见的 EWSR1-NFATC2 基因重排，对应于 t(20;22)基因易位。我们提出了一例在年轻女性皮下组织中发生的 EWSR1-NFATC2 基因融合的肿瘤。肿瘤表现为丰富的黏液样和纤维基质内的上皮样细胞条索状和小梁状结构。细胞对 NKX2.2、可变 CD99、角蛋白和上皮膜抗原表现出强烈的免疫反应性，但对 S100 和肌上皮标志物呈阴性。重要的是，与先前报道的病例一样，该患者的临床病程比尤文肉瘤更为惰性。该病例强调了 EWSR1-NFATC2 基因融合相关肿瘤的独特临床病理特征，使其与尤文肉瘤相区别。
