Current available guidelines in metastatic HER2 positive breast cancer designs a sequence of treatment with first-line double blockade with trastuzumab plus pertuzumab and a taxane according to Cleopatra trial results [1] and second-line treatment with trastuzumab emtansine (T-DM1) enforced by Emilia trial results [2] and, then, lapatinib plus capecitabine [3]. The gene discussed is ERBB2; the disease is breast carcinoma.