TTF1 and lung adenocarcinoma: In the light of the fact that the results of several other authors correspond to ours with regard to TTF-1 expression in colonic and gastric adenocarcinomas, some investigators have suggested to resolve the diagnostic dilemma in terms of the distinction of primary lung adenocarcinoma from metastatic colonic carcinomas using “gastrointestinal immunohistochemical markers” [8,9,11,36,37,38,39,40,41,42].