Frequency of ALDH+ cells in benign ductules of post-menopausal women with and without HRT at the time of surgery. Representative images of tissue from post-menopausal women are presented that demonstrate the significantly increased frequency of ALDH+ cells in breast tissue from women receiving HRT treatment at the time of surgery. A, Image illustrating the relatively high number of TDLUs containing ALDH+ cells (arrows) in benign breast tissue from a 70-year-old woman receiving HRT at the time of cancer surgery. B, Image of benign breast tissue from a 74-year-old woman who was not receiving HRT at the time of surgery, showing the presence of relatively few or complete absence of ALDH+ cells (white arrows indicate ductules with no ALDH+ cells). The benign tissue from this woman also contained ALDH+ stromal cells, as demonstrated in all patient groups. Scale bars: 100 μm.