For ER-positive BC cases, genetically raised MCP1 (OR: 1.08; 95% CIs: 1.03–1.13; P value: 2.70 × 10−3), MIP1b (OR: 1.02; 95% CIs: 1.00–1.04; P value: 0.012) and IL13 (OR: 1.05; 95% CIs: 1.01–1.09; P value: 0.024) were consistently associated with increased BC risk. Here, IL13 is linked to breast cancer.