Histiocytic sarcoma (HS), an extremely rare malignancy, usually follows a progressive time course, and patients die within two years of diagnosis. At present, there is no consensus for effective chemotherapy.

We report the case of a 54-year-old man who presented with low back pain and left hip joint pain. Imaging for the pain revealed multiple lesions in the mediastinum, vertebral bodies, and left ilium. Biopsies of the mediastinal and vertebral lesions yielded a diagnosis of soft tissue sarcoma. He received standard chemotherapy for sarcoma with doxorubicin and ifosfamide, as the initial pathological diagnosis was soft tissue sarcoma. This is called AI therapy and commonly used for soft tissue sarcoma. Palliative radiation therapy to the left iliac lesion was added for pain control.

Complete remission (CR) was achieved after two courses of AI therapy. Subsequent immunopathological examination revealed that the tumor was spindle cell dominant HS. CR was maintained for more than three years.

To the best of our knowledge, this is the first report that a CR was achieved by AI therapy as first-line treatment for spindle cell dominant HS, combined with focal bone palliative irradiation. AI therapy could be an effective option as chemotherapy for HS.

组织细胞肉瘤 (HS) 是一种极为罕见的恶性肿瘤，通常具有渐进性的时间进程，患者在诊断后两年内死亡。目前，对于有效的化疗还没有达成共识。

我们报告了一名 54 岁男性的病例，他因腰痛和左髋关节疼痛就诊。疼痛成像显示纵隔、椎体和左髂骨有多个病变。纵隔和脊椎病变的活检诊断为软组织肉瘤。他接受了多柔比星和异环磷酰胺的标准肉瘤化疗，因为最初的病理诊断是软组织肉瘤。这称为 AI 疗法，通常用于软组织肉瘤。为了控制疼痛，增加了对左侧髂骨病变的姑息性放射治疗。

两个疗程的 AI 治疗后达到完全缓解 (CR)。随后的免疫病理学检查显示肿瘤为梭形细胞显性HS。CR 维持了三年多。

据我们所知，这是第一次通过 AI 治疗作为梭形细胞显性 HS 的一线治疗与局灶性骨姑息性照射相结合实现 CR 的报告。AI 疗法可能是作为 HS 化疗的有效选择。