Chromophobe renal cell carcinoma with sarcomatoid change: A case report

Chromophobe renal cell carcinoma (ChRCC) is a rare type of kidney cancer that is generally associated with a favorable prognosis. By contrast, RCC with sarcomatoid transformation exhibits a more aggressive clinical course, with its pathogenesis remaining largely unclear. The present study reports a case of ChRCC with sarcomatoid changes. A 54-year-old woman presented to the Department of Urology for evaluation of an incidentally detected left renal mass. Histological examination of the resected tumor revealed two distinct components: One with conventional ChRCC morphology and the other comprising highly pleomorphic, poorly differentiated cells. Next-generation sequencing of the two components revealed chromosomal losses in multiple chromosomes and variations in the <i>RNF46</i> gene. Based on these findings, a final diagnosis of ChRCC with sarcomatoid changes was made. Although the two components shared some genetic changes, differences were also noted. The sarcomatoid area change carried chromosomal gain, single nucleotide variants and <i>MET</i> fusion compared with the conventional ChRCC component. Furthermore, while programmed cell death ligand 1 expression was negative in the conventional ChRCC component, >10% of the tumor cells in the sarcomatoid component were positive. Overall, the present case reveals novel genetic and immunohistochemical features of ChRCC with sarcomatoid changes.