KRT7 and adenocarcinoma: On immunohistochemistry (IHC), malignant cells (adenocarcinoma) within the tumor were positive for cytokeratin 7 (CK 7), cytokeratin 20 (CK 20), CEA, and caudal-related homeobox gene 2 (CDX 2) (Figure 3), but negative for thyroid transcription factor-1 (TTF-1), calretinin, cytokeratin 5/6 (CK 5/6), Wilms' tumor gene (WT-1) and vimentin (data not shown), supporting the diagnosis of gastrointestinal adenocarcinoma.