Furthermore, the large sample size allowed us to evaluate its prognostic value in a number of breast cancer subtypes including ER+ (node-negative and node-positive), ER–, ER+ and/or PR+ (HER2+ or HER2–), ER–/PR– and HER2+ (i.e. HER2-enriched) and triple-negative breast cancers. This evidence concerns the gene ERBB2 and breast cancer.