Collectively, the 10 mammary tumor-bearing Her2t/w/Adamts18−/− mice were all accompanied by metastases, while the 2 Her2t/w/Adamts18+/+ mice exhibited only primary mammary tumors (Additional file 1: Table S2), suggesting that ADAMTS18 deficiency increases the risk of HER2-positive spontaneous mammary metastasis. This evidence concerns the gene ERBB2 and breast cancer.