Compared with homozygous Her2t/t mice, heterozygous Her2t/w mice had significantly lower incidence of mammary tumors and longer average tumor latency, which may be more helpful for observing the synergistic effect of Adamts18 gene knockout on the process of mammary tumorigenesis and malignant progression in HER2-overexpressing mice. This evidence concerns the gene ERBB2 and neoplasm.