Sarcomatoid renal cell carcinoma: a comprehensive review of the biology and current treatment strategies.

Recent advancements in the molecular characterization of renal cell carcinoma altered the classification system and now kidney cancer is divided into several distinct histologic subtypes. Although once a separate histologic category, sarcomatoid renal cell carcinoma is no longer considered a separate tumor type because it can occur with all histologic subtypes. Limited research on tumors with sarcomatoid change has led to minimal progress in the understanding and treatment of these tumors. Because the sarcomatoid variant of renal cell carcinoma can account for approximately one in six cases of advanced kidney cancer, we hope to familiarize clinicians with these tumors by describing the historic background, histologic features, molecular characterization, diagnosis, prognosis, treatment strategies, and active clinical trials of this aggressive type of tumor.