Chromophobe renal cell carcinoma with sarcomatoid differentiation: A case report with molecular analysis

Abstract

Abstract Background Chromophobe renal cell carcinoma is a rare type of kidney cancer with a favorable prognosis. Renal cell carcinoma with sarcomatoid change has a more aggressive clinical course with unelucidated pathogenesis. Case presentation A 54-year-old female patient presented to the urology department for evaluation of an incidentally detected left renal mass. Computed tomography demonstrated a 13x10-cm mass in the left upper pole of the kidney. The resected tumor was clearly divided into two distinct components: one showed conventional Chromophobe renal cell carcinoma morphology, while the tumor cells of the other were highly pleomorphic with poorly differentiated morphology. The poorly differentiated component showed immunohistochemical expression for cytokeratin. Next-generation sequencing (NGS) of the two components shared multiple chromosomal losses and variation in the RNF46 gene. Based on these findings, we diagnosed the tumor as Chromophobe renal cell carcinoma with sarcomatoid change. Although the two components shared some genetic changes, there were also significant differences. The area of sarcomatoid change carried chromosomal gain, single nucleotide variants, and MET fusion compared with the conventional Chromophobe renal cell carcinoma component. Furthermore, while PD-L1 was negative in the conventional Chromophobe renal cell carcinoma component, more than 10% of the tumor cells in the sarcomatoid component were PD-L1 positive. Conclusion This case reveals novel genetic features of chromophobe renal cell carcinoma with sarcomatoid change.