A right pleural drain was positioned and the pleural liquid underwent cytological examination that revealed the presence of TTF1+ tumor cells; the following bronchoscopy aimed to carry out histological characterization of a parietal pleural nodule confirmed the diagnosis of CK7+/TTF1+/WT1—adenocarcinoma, with immunohistochemistry (IHC) compatible with a pulmonary origin. The gene discussed is TTF1; the disease is neoplasm.