Comparison with a large breast cancer gene expression dataset (METABRIC) showed that LDHA and SLC16A1 (MCT1) expressions are significantly correlated with expression of the hypoxia markers CAIX and HIF1A and that overexpression of the hypoxia markers CAIX and LDHA is significantly associated with shorter OS and relapse-free survival in breast cancer. This evidence concerns the gene SLC16A1 and breast cancer.