The MR (p = 0.0003, HR = 0.89, 95% CI = 0.84–0.95) and AE (p = 0.0006, HR = 0.92, 95% CI = 0.87–0.96) data indicated that low PLIN1 expression is associated with poor prognosis for breast cancer. This evidence concerns the gene PLIN1 and breast cancer.