CCL19 and breast cancer: CCR7/CCL19 promotes the development of systemic tumors such as BC [17], pancreatic cancer [18], melanoma [19], non-small cell lung cancer [20] and gastric cancer [21], and mediates the movement of dendritic cells to lymphoid organs playing an important role in the immune response and the transport and homing of lymphocytes to lymph nodes [22–24].