Frequency of ALDH+ cells in benign ductules of pre-menopausal women with different parities. Representative images of benign ductules in pre-menopausal patients demonstrate a significant decrease in frequency of ALDH+ cells (brown) with increasing parity in this patient subgroup. A, Image illustrating the relatively large number of ductular ALDH+ cells (arrows) in breast tissue from a 39-year-oldnulliparous woman. B, Image of breast tissue from a 38-year-old two-parous woman showing therelatively small number of TDLUs containing ductular ALDH+ cells (arrow), and scattered ALDH+ cells in the stroma. C, Image revealing the lack of ductular ALDH+ cells in breast tissue from a 41-year-old four-parous woman. Scale bars: 100 μm.