Abstract
INTRODUCTION: Immune checkpoint inhibitors (ICIs) are useful in the treatment of metastatic renal cell carcinoma. ICIs have been associated with a variety of immune-related adverse events (irAEs), one of which is a sarcoid-like reaction (SLR). SLR is often difficult to distinguish from cancer progression. CASE PRESENTATION: The patient is a 71-year-old woman. She underwent laparoscopic nephrectomy after 4 courses of ipilimumab + nivolumab therapy for clear cell renal cell carcinoma with femoral bone metastasis. In the pathological examination, in addition to tumor-infiltrating lymphocytes, numerous non-caseating epithelioid cell granulomas were found in the tumor. The occurrence of non-caseating epithelioid cell granuloma in a patient who did not meet the diagnostic criteria for systemic sarcoidosis was considered SLR due to ICI. CONCLUSIONS: We report the first case of a patient who underwent surgery for metastatic renal cell carcinoma after treatment with ICI and who was pathologically diagnosed with SLR in the kidney.