The heterogeneity of CAFs. The CAFs in breast cancer TME are mainly classified into myCAF, iCAF, and apCAF based on their heterogeneity. MyCAFs exhibit elevated expression of α-SMA, HAS2, and COL I, typically distributed in clusters. ICAFs exhibit elevated expression of IL-6, IL-8, and LIF, typically distributed near blood vessels. ApCAFs exhibit elevated expression of MHC II molecules and CD74, distributed in a scattered pattern. MyCAF promotes tumor invasion and metastasis by remodeling the ECM, while iCAF regulates immune responses in TME and facilitates the infiltration of immune cells. ApCAFs modulate the immunosuppressive microenvironment in an antigen-dependent manner. MyCAF, myofibroblastic cancer-associated fibroblast; apCAF, antigen-presenting cancer-associated fibroblast; iCAF, inflammatory/growth factor-rich cancer-associated fibroblast; α-SMA, α-smooth muscle actin; HAS2, hyaluronan synthase 2; COL I, type I collagen; IL-6, interleukin-6; IL-8, interleukin-8; LIF, leukemia inhibitory factor; MHC Ⅱ, class Ⅱ major histocompatibility complex; CD74, CD74 molecule.