CD4 and breast cancer: To further reveal the landscape of TME, an analysis of immune-infiltrating cells in the TME of BC as defined by FMI in the training set was accomplished, the result of which uncovered that activated memory CD4+ T cells and macrophages M0 and M1 were notably strengthened in the TME of the high-FMI group, while activated natural killer (NK) cells, monocytes, resting dendritic cells (DCs), and resting mast cells were markedly activated in the low-FMI group (Figure 6D).