Cytoreductive Nephrectomy After Combination of Nivolumab Plus Ipilimumab for Mucinous Tubular and Spindle Cell Carcinoma of the Kidney With Bone Metastases: A Case Report

Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare subtype of renal cell carcinoma and generally considered a low-grade renal epithelial neoplasm. However, MTSCC with distant metastases often shows a poor prognosis. This is the first reported case of cytoreductive nephrectomy after nivolumab plus ipilimumab combination treatment. A 26-year-old man had a 72-mm tumor at the left kidney with multiple osteolytic bone metastases. A biopsy of the renal tumor and bone metastases resulted in the diagnosis of MTSCC of the kidney with bone metastases. After nivolumab plus ipilimumab combined treatment, he underwent cytoreductive nephrectomy. The excised specimen showed higher PD-L1 expression in the spindle components than in the tubular components, but CD4- and CD8-positve T-cells showed greater infiltration in the tubular components than the spindle components. Combination immunotherapy of nivolumab and ipilimumab may be an effective treatment option for metastatic MTSCC of the kidney.