AR and breast cancer: Following the identification of the major intrinsic molecular subtypes of breast cancer (i.e., luminal type A, luminal type B, TNBC, HER2+) [4], additional molecular TNBC subtypes were identified, such as the claudin-low subtype, characterized by an epithelial-to-mesenchymal transition (EMT) phenotype [5] and the apocrine subtype, which exhibits activation of the androgen receptor (AR) pathway [6].