ERBB2 and breast cancer: This result is also consistent with another study in breast cancer, in which CEACAM6 is strongly associated with the development of invasive breast cancer in atypical ductal hyperplasia [31], and in the breast cancer molecular subtype HER2 overexpression (HER2-OE): The expression of CEACAM6 was highest in ER− , PR− , HER2 + , CK5/6 ± types, before which a functional synergy between HER2 and TGF-β had been demonstrated.