Stem cell traits in a subpopulation of mammary tumor cells are thought to be implicated in treatment resistance (Dean et al, 2005) and metastasis dissemination (Malanchi et al, 2012; Rosenthal et al, 2012; Visvader & Lindeman, 2012) and high levels of Pin1 correlate with high grade breast cancer and chemoresistance (Wulf et al, 2001; Ding et al, 2008; Kim et al, 2009; Girardini et al, 2011). This evidence concerns the gene PIN1 and breast cancer.