CD99 and breast cancer: Ulteriorly, the interaction of each intracellular pathway within distinctive groups was identified, witnessing that most of the signaling pathways were notably active in normal populations, such as SELE, ANGPT, CCL, ANGPTL, and other twenty pathways, whereas the activation of seven pathways, namely APP, MIF, MK, ESAM, PECAM1, CD99 and SPP1, primarily occurred in BC patients (Figure 4C).