Despite more than 30 HER2 phosphorylation (pHER2) sites reported in PhosphoSitePlus®10 and the availability of antibodies directed against at least 11 of these sites, the abundance of pHER2 at only three phosphorylated sites has been analyzed by IHC in BC patients to date, and this by a few studies only. Here, ERBB2 is linked to breast cancer.