Recently, Gao et al. identified and characterized a subtype of CAFs which particularly has the presence of the cell surface protein CD63; these CD63+ CAFs are capable of secreting exosomes enriched in miR-22, which can bind to their targets, ERα and PTEN, and deregulate their expression, thus conferring tamoxifen resistance to breast cancer cells (Gao et al., 2020). This evidence concerns the gene CD63 and breast cancer.