BCOR-rearranged sarcomas are rare and belong to the Ewing-like sarcomas (ELS). Their morphology and histopathological features make the diagnosis challenging. We present a case, initially diagnosed as an unusual extraskeletal myxoid chondrosarcoma (EMC). A 54-year-old male patient developed an asymptomatic swelling of the lower leg. Imaging showed a 9.5-cm large intramuscular soft tissue mass. Due to its morphological and immunohistochemical profile on biopsy, it was initially diagnosed as an EMC. The patient was treated by complete resection and adjuvant radiotherapy and remained free of tumor at 7 years follow-up. Using next-generation sequencing (NGS), we retrospectively identified RGAG1-BCOR gene fusion (confirmed by RT-PCR), which has not been described in somatic soft tissue tumors so far. This finding broadens the spectrum of partner genes in the BCOR-rearranged sarcomas in a tumor with a well-documented, long clinical follow-up.

BCOR重排肉瘤罕见，属于尤文样肉瘤 (ELS)。它们的形态学和组织病理学特征使诊断具有挑战性。我们介绍了一个病例，最初被诊断为不寻常的骨外粘液样软骨肉瘤 (EMC)。一名 54 岁男性患者出现小腿无症状肿胀。成像显示一个 9.5 厘米大的肌肉内软组织肿块。由于活检的形态学和免疫组织化学特征，它最初被诊断为 EMC。该患者接受了完全切除和辅助放疗，并在 7 年随访时保持无肿瘤。使用二代测序（NGS），我们回顾性鉴定了RGAG1-BCOR基因融合（通过 RT-PCR 确认），迄今为止尚未在体细胞软组织肿瘤中描述。这一发现拓宽了肿瘤中BCOR重排肉瘤中伴侣基因的范围，并有充分记录的长期临床随访。