CCL19 and breast cancer: In the analysis of breast cancer survival, we found a potential causal effect of plasma CCL19 on breast cancer survival (HR = 0.85, 95% CI = 0.75–0.96, p < 0.01), especially for ER-positive breast cancer patients (HR = 0.82, 95% CI = 0.70–0.97) (Figure 2; Supplementary Table S4).