ERBB2 and breast cancer: To elucidate the role of ADAMTS18 in HER2-positive mammary tumorigenesis and metastasis in vivo, we compared the incidence of mammary tumor and metastasis between Adamts18-knockout (MMTV)-Her2/ErbB2/Neu+ transgenic mice (i.e., Her2t/w/Adamts18−/−) and Adamts18-wildtype (MMTV)-Her2/ErbB2/Neu+ transgenic mice (i.e., Her2t/w/Adamts18+/+).