In order to model human breast tumorigenesis several Wnt/β-catenin pathway-related mouse models have been generated, and it is believed that tumours originate from stem cells and/or progenitor cells (e.g. MMTV-Wnt1, MMTV-Wnt10b and MMTV-ΔN-β-catenin amongst others; Wend et al, 2011). The gene discussed is WNT1; the disease is neoplasm.