In the cohort and case–control analysis [17, 18, 28, 33, 36, 38, 42, 44, 60, 65, 70, 72, 73, 80], any use of HRT was associated with higher risk in all BC subtypes: all seven luminal A studies [17, 33, 38, 42, 70, 72, 73] and lower risk among subgroups of estrogen and progesterone therapy (≤ 5 years vs. never) [17] and women with BMI < 25 [33], higher risk in three [17, 38, 72] luminal B studies, four [36, 42, 60, 72] HER2-overexpressing studies and six [17, 19, 33, 38, 42, 72] TNBC studies. This evidence concerns the gene ERBB2 and breast cancer.