To investigate whether a different expression of miR-9 could play a role in the acquisition of normal fibroblasts to a cancer-associated fibroblast phenotype, the level of mature miR-9 was first evaluated in couples of primary NFs/CAFs isolated from patients with different breast cancer subtypes (luminal-A, luminal-B, HER2 and triple negative). Here, ERBB2 is linked to breast cancer.