肉瘤样癌是一种罕见的高级别恶性肿瘤，具有上皮和间充质组分。它可能是免疫疗法的良好选择，因为与程序性细胞死亡配体1的过度表达相关。上尿路肉瘤样癌（UC）极为罕见。在这里，我们报告了一例对免疫疗法有反应的肾盂肉瘤样UC的首例病例。一名79岁男性被转介到我们医院，抱怨各种症状，包括食欲缺乏和腹痛。经过计算机断层扫描，发现右心房肿瘤，左肾9厘米的肿块，肾静脉肿瘤栓，近主动脉淋巴结肿大和多个小的肺结节。患者接受了右心房肿瘤的切除手术。肿瘤的病理学分析即使进行了多轮免疫组化也没有得出准确的诊断。他接受了左肾的穿刺活检，并最初被诊断为集管癌，一种罕见的肾细胞癌亚型。在初步诊断后，使用尼伏单抗和伊匹单抗进行了免疫疗法。此后，包括左肾肿瘤在内的几乎所有病变大小都有所减小。然而，由于多次左肾出血，他在开始免疫疗法约一年后接受了左肾切除手术。切除标本的组织学检查发现了两种癌症形式-肉瘤样UC和传统的高级别UC。手术后两个月，患者发现了新的肺部转移灶。他接受了吉西他滨和顺铂化疗，随后进行了帕博利珠单抗免疫疗法。然而，这两种治疗都无效。患者在第一次住院后的19个月内死于癌症。本文介绍了一例对免疫疗法有部分反应的肾盂肉瘤样UC，表明免疫疗法可能是肉瘤样UC的一种有前途的治疗方法。©2023年作者。

Sarcomatoid carcinoma is a rare, high-grade malignancy with epithelial and mesenchymal components. It may be a good candidate for immunotherapy because it is associated with overexpression of programmed cell death ligand 1. Sarcomatoid urothelial carcinoma (UC) of the upper urinary tract is extremely rare. Here we report the first case of sarcomatoid UC of the renal pelvis that responded to immunotherapy.A 79-year-old man was referred to our hospital complaining of various symptoms, including anorexia and abdominal pain. A computed tomography scan revealed a right atrial tumor, a 9 cm left renal mass with a renal vein tumor thrombus, para-aortic lymphadenopathy, and multiple small lung nodules. The patient underwent resection of the right atrial tumor. Pathological analysis of the tumor did not lead to an accurate diagnosis even after several rounds of immunohistochemistry. He underwent a needle biopsy of the left kidney and was initially diagnosed with collecting duct carcinoma, a rare subtype of renal cell carcinoma (RCC). Following the initial diagnosis, immunotherapy with nivolumab and ipilimumab commenced. Thereafter, almost all lesions, including the left renal tumor, were reduced in size. However, he underwent a left nephrectomy approximately a year after beginning immunotherapy due to repeated left renal bleeding. Histological examination of the nephrectomy specimen revealed two forms of cancer-sarcomatoid UC and conventional high-grade UC. Two months after surgery, the patient was found to have new lung metastases. He underwent chemotherapy with gemcitabine and cisplatin, followed by immunotherapy with pembrolizumab. However, both treatments were ineffective. The patient died of cancer 19 months after his first admission.The presented case of sarcomatoid UC of the renal pelvis that partially responded to immunotherapy suggests that immunotherapy can be a promising treatment for sarcomatoid UC.© 2023. The Author(s).