组织细胞肉瘤（HS）是一种罕见的造血系统肿瘤，具有侵袭性临床病程且对常规化疗反应不佳。目前，没有可用的标准治疗范例。在此，我们介绍了一个使用派姆单抗联合 GDP 方案（吉西他滨、顺铂和地塞米松）治疗的新发 HS 病例，该病例获得持续完全缓解，无进展生存期超过 4 年。免疫组织化学分析表明，活检样本中程序性死亡配体 1 (PD-L1) 显着过度表达。此外，使用 JAK-2 探针的荧光原位杂交 (FISH) 显示 9p24.1 扩增，表明对 JAK-STAT 途径的依赖。聚合酶链反应 (PCR) 分析未发现任何 BRAF-V600 突变。因此，免疫检查点抑制剂 (ICI) 与化疗同时使用，导致持续完全缓解和无进展生存期超过 4 年。我们的研究结果表明，ICI 和化疗相结合可能是治疗 HS 的一种有前途的治疗方法。

Histiocytic sarcoma (HS) is a rare hematopoietic neoplasm with an aggressive clinical course and a poor response to conventional chemotherapy. Currently, no standard treatment paradigms are available. Herein, we present a case of de novo HS treated with pembrolizumab combined with a GDP regimen (gemcitabine, cisplatin, and dexamethasone) that resulted in sustained complete remission with progression-free survival exceeding 4 years. Immunohistochemical analysis demonstrated significant overexpression of programmed death ligand 1 (PD-L1) on biopsy samples. Additionally, fluorescence in situ hybridization (FISH) with a JAK-2 probe indicated 9p24.1 amplification, suggesting reliance on the JAK-STAT pathway. Polymerase chain reaction (PCR) analysis did not reveal any BRAF-V600 mutations. Consequently, an immune checkpoint inhibitor (ICI) was administered alongside chemotherapy, resulting in sustained complete remission and progression-free survival for over 4 years. Our findings suggest that a combination of ICI and chemotherapy could represent a promising therapeutic approach for HS.