WNT1 and neoplasm: Historical models of spontaneous and mouse mammary tumour virus (MMTV)-infected tumours (Fig. 1) do not share histological features of human tumours (Cardiff et al., 2004) while specific oncogenic models in the form of conventional GEMMs (e.g. MMTV-Wnt1 and MMTV-PyMT) can demonstrate phenotypic similarities as well as disparities (Cardiff and Wellings, 1999).