BackgroundInflammatory myofibroblastic tumors (IMTs) are rare mesenchymal soft tissue sarcomas that often present diagnostic challenges due to their wide and varied morphology. A subset of IMTs have fusions involving ALK or ROS1. The role of next‐generation sequencing (NGS) for classification of unselected sarcomas remains controversial.Methods and ResultsWe report a case of a metastatic sarcoma in a 34‐year‐old female originally diagnosed as an unclassified spindle cell sarcoma with myofibroblastic differentiation and later reclassified as IMT after NGS revealed a TFG‐ROS1 rearrangement. Histologically, the neoplasm had spindle cell morphology with a lobulated to focally infiltrative growth pattern with scant inflammatory cell infiltrate. Immunohistochemistry demonstrated focal desmin and variable smooth muscle actin staining but was negative for SOX10, S100, and CD34. Fluorescence in situ hybridization was negative for USP6 or ALK gene rearrangements. NGS revealed a TFG‐ROS1 rearrangement and the patient was treated with crizotinib with clinical benefit.ConclusionsWe discuss the role of NGS as well as its potential benefit in patients with unresectable, ALK‐negative metastatic disease. Considering this case and previous literature, we support the use of NGS for patients requiring systemic treatment.

中文翻译：

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识别 TFG-ROS1 融合后梭形细胞肉瘤的重新分类：证明新一代测序在肉瘤中的临床益处的案例

背景炎症性肌纤维母细胞肿瘤（IMT）是罕见的间叶性软组织肉瘤，由于其广泛且多样的形态，常常给诊断带来挑战。 IMT 的一个子集具有融合，涉及ALK 或 ROS1。下一代测序 (NGS) 在未选择的肉瘤分类中的作用仍存在争议。方法和结果我们报道了一名 34 岁女性的转移性肉瘤病例，最初诊断为未分类的梭形细胞肉瘤，伴有肌纤维母细胞分化，后来重新分类NGS 揭示后作为 IMTTFG-ROS1重新排列。在组织学上，肿瘤具有梭形细胞形态，具有分叶状至局灶性浸润性生长模式，且很少有炎性细胞浸润。免疫组织化学显示局灶结蛋白和可变平滑肌肌动蛋白染色，但 SOX10、S100 和 CD34 呈阴性。荧光原位杂交结果为阴性美国药典6或者ALK基因重排。 NGS 揭示了TFG-ROS1重排，患者接受克唑替尼治疗并获得临床获益。结论我们讨论了 NGS 的作用及其在不可切除、ALK‐阴性转移性疾病。考虑到该病例和之前的文献，我们支持对需要全身治疗的患者使用NGS。