MUC5B and breast cancer: HC are lined with a single-, or stratified layer of KRT (keratin)5 + basal cells (BC) or by a stratified bronchiolar-like epithelium composed of KRT5 + basal-, acetylated tubulin (AcTub) + ciliated-, and secretory epithelial cells, mainly expressing MUC (mucin) 5B [4–9].