ERBB2 and breast carcinoma: In contrast, immunohistochemical (IHC) staining profile is a cost‐effective and popular surrogate.5 Based on IHC staining profiles, St Gallen International Breast Cancer Conference in 2013 classified breast cancer into four subtypes: Luminal A, Luminal B, HER2‐positive, and triple‐negative breast cancer (TNBC).