ERBB2 and breast cancer: We found positive associations between an SD increase in BT and luminal A-like BC and luminal B/HER2-negative-like BC risks (OR 1.29, 95% CI 1.15–1.43 and OR 1.22, 95% CI 1.07–1.40) with consistent directions of association found using the weighted median, weighted mode and MR-Egger approaches for the association with luminal A-like BC.