In the studies providing data on BC among young women, higher number of childbirths and younger age at FFTP were associated with a decreased risk of luminal BC (ER+ or PR+ and HER2−), but not of TN tumors, while duration of breastfeeding was associated with a protective effect in both luminal and TN BC, as observed in the overall analyses13,14. This evidence concerns the gene ERBB2 and breast cancer.