ERBB2 and invasive ductal breast carcinoma: She was recently diagnosed with stage 1 breast invasive ductal carcinoma (IDC) according to the American Joint Committee on Cancer [AJCC] Cancer Staging Manual (7): the tumor was characterized by neoplastic cells positive for the expression of estrogen receptors (80%), progesterone receptors (30%), and Ki67 (5%) and negative for the expression of HER2/neu.