Herein we described the clinical, radiological, histological, and molecular characteristics of seven soft tissue aneurysmal bone cysts (STABCs) diagnosed and managed at a tertiary cancer center and to elucidate their relationship with myositis ossificans (MO). All cases had established imaging and histopathological diagnosis of STABC and were subject to fluorescence in situ hybridization (FISH) for USP6 rearrangement and Archer® FusionPlex® targeted RNA sequencing (RNASeq) analysis to identify the fusion partner. A thorough literature review of STABC and MO was conducted. The patients presented with painful masses unpreceded by trauma, occurring most commonly in the deep soft tissue of the thigh/gluteus (4/7), and also in the supraclavicular region, the axilla, and the hand. On imaging, the lesions were frequently associated with peripheral calcification on conventional radiographs and CT (6/7), cystic components on ultrasound, as well as perilesional edema (7/7) and fluid levels (3/7) on MRI. Bone scan (1/1) showed intense radiotracer uptake. Histologically, 6/7 cases demonstrated zonal arrangements reminiscent of MO. USP6 rearrangement was found in all seven cases by FISH and/or RNASeq. RNASeq further detected COL1A1-USP6 fusion in six cases and a novel ANGPTL2-USP6 fusion in one case. Four patients underwent resection of the tumors and were disease free at their last follow-up. Three patients who underwent incisional or needle biopsies had no evidence of disease progression on imaging studies. In conclusion, the clinical, radiological, and pathological overlap between STABC and MO suggests that they are closely related entities. A novel fusion ANGPTL2-USP6 is associated with distinct clinical and pathological presentation.

在此，我们描述了在三级癌症中心诊断和治疗的七种软组织动脉瘤性骨囊肿 (STABC) 的临床、放射学、组织学和分子特征，并阐明它们与骨化性肌炎 (MO) 的关系。所有病例均已建立 STABC 影像学和组织病理学诊断，并接受USP6荧光原位杂交 (FISH)重排和 Archer® FusionPlex® 靶向 RNA 测序 (RNASeq) 分析以确定融合伴侣。对 STABC 和 MO 进行了全面的文献回顾。患者表现为无外伤史的疼痛肿块，最常见于大腿/臀肌 (4/7) 的深层软组织，以及锁骨上区域、腋窝和手部。在影像学上，病变通常与常规 X 光片和 CT 上的外周钙化 (6/7)、超声上的囊性成分以及 MRI 上的病灶周围水肿 (7/7) 和液位 (3/7) 相关。骨扫描 (1/1) 显示强烈的放射性示踪剂摄取。在组织学上，6/7 的病例表现出让人联想到 MO 的带状排列。美国药典6FISH 和/或 RNASeq 在所有 7 个案例中都发现了重排。RNASeq在 6 例中进一步检测到 COL1A1-USP6融合，在 1 例中检测到新的ANGPTL2-USP6融合。4 名患者接受了肿瘤切除术，并且在最后一次随访时没有疾病。三名接受切口或穿刺活检的患者在影像学研究中没有疾病进展的证据。总之，STABC 和 MO 之间的临床、放射学和病理学重叠表明它们是密切相关的实体。新型融合ANGPTL2-USP6与不同的临床和病理表现相关。