Similar to carcinogenesis in humans, mammary tumourigenesis in MMTV-erbB2 transgenic mice is a multistage process that proceeds through hyperplasia, mammary intraepithelial neoplasia (MIN, similar to human DCIS), and invasive cancer (Campiglio et al, 2004). The gene discussed is ERBB2; the disease is ductal breast carcinoma in situ.