Molecular phenotypying of breast cancer by Perou et al. [14] delineated four intrinsic-subtypes of breast cancer (Luminal, Basal, ERBB2+, and Normal Epithelial Group) based on 476 genes that showed variable expression in 40 breast cancer samples compared to 20 matched samples that had received doxorubicin treatment. Here, ERBB2 is linked to breast cancer.