To confirm the hypothesis of GATA3 silencing by DNMT3B-mediated DNA methylation in its promoter region, we established an independent validation cohort of 19 breast cancer patients from the Centre Léon Bérard, Lyon, France (biobank CRB-CLB BB-0033-00050, dataset registered as CMT 2023-22_BS2023_010_R201-004-415). This evidence concerns the gene DNMT3B and breast carcinoma.