Despite the diversity of genetic changes driving the different molecular subtypes, two different types of CSCs exist in any of the cHER2+ BC subtypes: a more proliferative, epithelial-like state characterized by the expression of the CSC marker ALDH, and a more quiescent and invasive, mesenchymal-like state characterized by the expression of the CD44+CD24−/low immunophenotype [56, 120] (Figure B1-2). Here, CD44 is linked to breast cancer.