Among these, TTF-1 is a pneumocyte marker with high sensitivity and specificity for primary lung adenocarcinomas [55,56,57,58,59,60,61,62]; TTF-1 is not expressed in every type of lung adenocarcinoma (Yoshimura) and, moreover, can also be positive in carcinomas from other sites, particularly depending on the antibody clone. Here, TTF1 is linked to lung adenocarcinoma.