With a focus on ECM POSTN, Bakhtyar et al. used IHC in xenograft models to illustrate that POSTN was found to coexist with α-SMA-expressing CAFs in the stroma of both local and metastasized CCRCC, indicating that CCRCC-associated POSTN was derived from stroma rather than tumors [109]. Here, POSTN is linked to nonpapillary renal cell carcinoma.