Many of the molecular features defining the human breast cancer sub-types have been shown, by DNA microarrays analysis, to be conserved in murine models.54 For example, 100% of C3(1)-Tag transgenic mice develop breast cancers and produce a “mixed” phenotype, with tumours expressing luminal, basal and mesenchymal genes akin to those seen in basal-like and luminal B human cancers.55 Our analyses demonstrated marked histological differences between tumours and control tissues from this model. The gene discussed is C3; the disease is cancer.