Fig. 2. The structure of the mammary epithelium. (A) Paraffin sections from a 10-week-old mouse mammary gland stained with hematoxylin-phloxin-safran dye. The surrounding fat pad is visible. (B) Paraffin section labelled with markers of epithelial luminal cells (anti-cytokeratin 8; green) and basal cells (anti-cytokeratin 14; purple). (C) Polarization of the luminal epithelium is illustrated by labeling for polarity markers zonula occludens 1 (ZO-1; apical, green) and β-catenin (βcat; basolateral, red). (D) Schematic representation of the structure of the mammary epithelium and the different integrin heterodimers expressed in luminal epithelial cells and myoepithelial cells.