S100A4 and nonpapillary renal cell carcinoma: Future studies incorporating additional fibroblast markers [17, 18, 20], such as α-smooth muscle actin (α-SMA) or fibroblast-specific protein-1 (FSP-1), in conjunction with epithelial and mesenchymal markers, would offer a more comprehensive characterization of the cell types involved and their contribution to ccRCC development and progression.