HDL-raising variants in CETP were associated with raised breast cancer risk (OR 1.07, 95% CI, 1.03–1.11, P = 0.001) and ER-positive breast cancer risk (OR 1.08, 95% CI, 1.03–1.13, P = 0.001), although in both cases, MR Egger was suggestive of a null association (OR 1.00, 95% CI, 0.87–1.15, P = 0.972; and OR 1.01, 95% CI, 0.86–1.17, P = 0.948, respectively). This evidence concerns the gene CETP and breast cancer.