We investigated parity, breastfeeding, and breast cancer risk by hormone-receptor (estrogen (ER) and progesterone receptor (PR)) and molecular subtypes (luminal A, luminal B, HER2-enriched, and basal-like) in the Nurses’ Health Study (NHS; 1976–2012) and NHSII (1989–2013). This evidence concerns the gene ERBB2 and breast cancer.