FN1 and nonpapillary renal cell carcinoma: Furthermore, Zvirblyte et al. identified that myofibroblasts in the TME of ccRCC express abundant ECM components, such as collagen types I, III, IV, and VI, as well as fibronectin, with enrichment of related markers like ACTA2 and tissue inhibitor of metalloproteinase (TIMP)1.