ACTA1 and neoplasm: CAFs are a subpopulation of fibroblasts found in the tumor microenvironment [3], They are myofibroblasts, or activated fibroblasts in the tumor stroma, mostly characterized by the expression of activated fibroblast markers, such as α-smooth muscle actin (α-SMA) and fibroblast activation protein-α (FAP-α) [4].