Several studies suggested that ALDH1 is associated with an aggressive phenotype and poor prognosis,[12–16] although others found that it was not a survival predictor of BC[17–19]; another study reported that expression of the major ALDH1 isoenzyme ALDH1A1 predicted a better outcome in BC of the triple-negative subtype.[20] The prognostic value of ALDH1 in BC is therefore controversial, and has not been fully elucidated. The gene discussed is ALDH1A1; the disease is breast cancer.