ERBB2 and neoplasm: Further immunohistochemistry showed the tumor was positive for cytokeratin 7 (CK7), CK20, villin, and ErbB2/HER2, but negative for gross cystic disease fluid protein-15 (GCDFP-15), ER, and PR (Figure 2C,D,E,F,G,H,I and Table 1).