Subgroup analysis further revealed that high EXO1 expression was associated with poor OS in specific subgroups of patients with BRCA, including those with T2 stage, N1 stage, M0 stage, pathologic stage II, luminal B subtype of PAM50 classification, age <60 years, and infiltrating ductal carcinoma histological type (Supplementary Figures S1A–G). Here, EXO1 is linked to invasive ductal breast carcinoma.