KRT7 and neoplasm: Immunohistochemically, tumor cells were positive for cytokeratin and vimentin, but negative for cytokeratin 7 (CK 7), thyroid transcription factor-1 (TTF-1), carbonic anhydrase-9 (CA-9), paired box gene 8 (PAX8), leukocyte common antigen (LCA), and human melanoma black 45 (HMB45) (Fig. 3B–D).