Department of Pathology, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA.
Department of Hematology/Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA.
Genes Chromosomes Cancer. 2021 Oct;60(10):709-712. doi: 10.1002/gcc.22976. Epub 2021 Jun 19.
Extraskeletal myxoid chondrosarcoma (EMC) is a rare sarcoma of uncertain differentiation, characterized by recurrent chromosomal translocation involving NR4A3 (9q22.33) in more than 90% of cases. Five fusion partners for NR4A3 have been described including: EWSR1 (22q12.2), TAF15 (17q12), FUS (16p11.2), TCF12 (15q21), and TFG (3q12.2). This report describes a patient with an EMC at the dorsum of the right foot. The tumor showed a cord-like and reticular pattern in a background of myxoid matrix. The tumor cells demonstrated an epithelioid morphology with prominent nucleoli. The tumor cells were positive for synaptophysin, GFAP, with focal positivity for CD117, S100, Cam5.2, and NSE, and negative for AE1/3, desmin, and SMA. An RNA next-generation sequencing test showed a SMARCA2-NR4A3 gene fusion which has not been previously reported. The exon 3 of SMARCA2 was fused to exon 3 of NR4A3. This fusion was confirmed by NR4A3 break-apart FISH, although both SMARCA2 (9p24.3) and NR4A3 (9q22.33) are located on chromosome 9. The tumor cells showed retained expression of INI1 and SMARCA2 by immunohistochemistry.
骨外黏液样软骨肉瘤（EMC）是一种分化不确定的罕见肉瘤，其特征在于超过 90%的病例中存在涉及 NR4A3（9q22.33）的反复染色体易位。已经描述了 NR4A3 的 5 种融合伴侣，包括：EWSR1（22q12.2）、TAF15（17q12）、FUS（16p11.2）、TCF12（15q21）和 TFG（3q12.2）。本报告描述了一名右足背部 EMC 患者。肿瘤在黏液样基质背景下呈索状和网状模式。肿瘤细胞具有明显核仁的上皮样形态。肿瘤细胞对突触素、GFAP 阳性，CD117、S100、Cam5.2 和 NSE 局灶性阳性，AE1/3、结蛋白和 SMA 阴性。RNA 下一代测序测试显示存在 SMARCA2-NR4A3 基因融合，这是以前未报道过的。SMARCA2 的外显子 3 与 NR4A3 的外显子 3 融合。尽管 SMARCA2（9p24.3）和 NR4A3（9q22.33）都位于染色体 9 上，但通过 NR4A3 断裂分离 FISH 证实了这种融合。肿瘤细胞通过免疫组化显示保留了 INI1 和 SMARCA2 的表达。
