Cytology of a sarcomatoid renal cell carcinoma with unusual coexpression of S-100 protein: a case report, review of the literature and cytologic-histologic correlation.

Sarcomatoid renal cell carcinoma (SRCC) is an aggressive variant of renal cell carcinoma; it is an uncommon, malignant neoplasm, and its diagnosis is usually based on the histologic evaluation of a nephrectomy specimen. Patients are treated with systemic therapy and, generally, a nephrectomy is not performed. Therefore, arriving at an accurate diagnosis is critical for planning further management.