Changes of CEACAM1 expression in different types of malignancies were contradictory; some reports pointed to a partial reduction or loss of CEACAM1 expression in breast cancer (Wang et al., 2011), while others demonstrated that CEACAM1 was expressed to the same extent in both normal and malignant breast tissues (Takeuchi et al., 2019). Here, CEACAM1 is linked to breast cancer.