Recurrent TFE3 ‐Rearranged Renal Cell Carcinoma Responding to Pembrolizumab Plus Lenvatinib After Postoperative Pembrolizumab: A Case Report

Introduction TFE3‐rearranged renal cell carcinoma (RCC) is rare, and evidence guiding systemic therapy is limited. Case Presentation A 25‐year‐old man with gross hematuria had a left renal tumor with hilar lymph node metastasis. Robot‐assisted radical nephrectomy and hilar lymph node dissection were performed. Histology, immunohistochemistry, and fluorescence in situ hybridization confirmed TFE3‐rearranged RCC, pT3aN1. Postoperative pembrolizumab was started because of the high risk of recurrence. Eight months after surgery, lung and retroperitoneal metastases developed. Lenvatinib was added to ongoing pembrolizumab. The metastatic lesions decreased within one month, and a partial response according to Response Evaluation Criteria in Solid Tumors has been maintained for ten months. Conclusion This case suggests that adding a vascular endothelial growth factor receptor tyrosine kinase inhibitor to pembrolizumab may be a therapeutic option for recurrent TFE3‐rearranged RCC, although longer follow‐up and molecular characterization are needed.