Additionally, when we included ALDH1A1 expression in the signature, EpCAMhighVIMlowALDH1A1high, its outcome prediction potential power was improved, remarking the need for the study of more cells markers besides EpCAM. In addition to its association with therapy failure, ALDH1A1 expression in tissue samples has been related to poor prognosis in different BC subtypes [63,64,65,66], and its expression in CTCs has also been linked with worse outcome in BC patients [23,26,28,32,67]. This evidence concerns the gene ALDH1A1 and breast cancer.