ESR1 and invasive ductal breast carcinoma: Among the 2 cases upgraded to IC, one was an invasive ductal carcinoma (IDC) pT1b (6 mm, HG3, ER 100%, PR 5%, HER2-negative, Ki67 55%) pN0sn, and the other was pT1a (IDC, 2 mm, HG2, ER 100%, PR 100%, HER2-negative, Ki67 5%) N0 (Table 7).