Marcato et al. [28] reported that an increased ALDH activity in breast cancer stem cells is due to the effects of the isoform ALDH1A3, while Chen et al. [29] reported that ALDH1B1 is more profoundly expressed in adenocarcinomas than ALDH1A1, although the function and the cellular localization of ALDH1L2 remain unknown. This evidence concerns the gene ALDH1B1 and breast cancer.