KRT20 and lung adenocarcinoma: Immunohistochemical staining was positive for thyroid transcription factor 1 (TTF-1) (Figure 3), cytokeratin 7 (CK7) and mucin 1 cell surface associated (MUC1), while negative for cytokeratin 20 (CK20), and CD15, thus suggesting bladder metastasis from lung adenocarcinoma.