ERBB2 and neoplasm: Because the primary tumor was HER2 positive (immunohistochemistry (IHC) 2 + /fluorescence in situ hybridization-positive), S-1 + CDDP + trastuzumab chemotherapy (S-1 80 mg day 1–21, CDDP 30 mg/m2 day 8, trastuzumab 174 mg) [5] was performed.