Only a few contact‐dependent pathways have been reported thus far, which include EphA4/Ephrin and CD90/CD11b signaling pathways for breast cancer stem cells, and an ICAM1/integrin signaling for ovarian cancer spheroids.[45, 46] Therefore, the metadherin/CEACAM1 signaling between metastatic cells and macrophages identified here has provided further new insights in targeting this tumor–immune interaction. This evidence concerns the gene MTDH and breast cancer.