ERBB2 and ductal breast carcinoma in situ: Histopathologically, the classic progression model of human BRDC was a linear multi‐step process that initiates as ductal hyperplasia (DH), progresses to ductal carcinoma in situ (DCIS), and evolves into invasive ductal carcinoma (IDC).[5] IDC was classified into four major clinical subtypes: luminal A, luminal B, HER2‐enriched, and TNBC based on histopathological criteria including the expression of hormone receptors (estrogen receptor and/or progesterone receptor) and/or human epidermal growth factor receptor 2 (HER2).[6]