Among postmenopausal, hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer patients treated for dyslipidaemia, the good serum lipid control group had significantly better RFS (p = 0.014, log-rank), lower postoperative NLR (p = 0.012), and higher TILs in resected tissues (p = 0.024) than the poor control group. Here, ERBB2 is linked to inherited lipid metabolism disorder.