TTF1 and adenocarcinoma: Gastric endoscopy pathology revealed adenocarcinoma in the gastric body, and based on immunohistochemistry and patient history, the tumor was suspected to originate from lung adenocarcinoma; immunohistochemistry staining results were as follows: TTF-1 (+), Napsin-A (+), CK7 (weakly positive), CDX2 (−), CK20 (−), and Ki-67 (60%+) (Fig. 3A–F).