In breast tumours, an embryonic stem cell (ES)-like signature characterized by activation of targets of Nanog, Oct4 and Sox2 is associated with high-grade ER-negative tumours and with aggressive tumour behaviour (Ben-Porath et al,2008), supporting the possibility that ES genes contribute to the stem cell-like phenotype found in many tumours. The gene discussed is POU5F1; the disease is breast neoplasm.