A variety of biological tumor markers for breast cancer have been investigated, such as CEA [12]–[14], CA 153[15]–[16], CA27.29 [17], [18], CA549 [19], Her2 [20]–[24], Cytokeratin8/18 [25], [26], CYFRA21-1[27]–[29], TPS [30]–[32], TPA [33] and other markers. Here, CEACAM5 is linked to breast cancer.