Figure 1

Photomicrographs of human mammary tissue during the follicular and luteal phases of the natural menstrual cycle. (a,b) Ki-67 expression (arrows and/or deep brown color) in epithelial cells from normal mammary lobule of a representative patient in the follicular phase (a) and in the luteal phase (b). (c–f) TdT-mediated dUTP nick end labelling (TUNEL)-positive staining (arrows, deep brown color) indicating apoptotic epithelial cells from representative patients in the follicular phase (c,d) and in the luteal phase (e,f); (f) high magnification of a labeled cell displaying the characteristic features of chromatin condensation and apoptotic bodies.