His diagnostic biopsy (a para-aortic lymph node) contained sheets of polygonal poorly differentiated adenocarcinoma cells that were positive for lung markers, thyroid transcription factor (TTF1), and cytokeratin7 (CK7) and negative for p40 (squamous marker), CD56, chromogranin A, synaptophysin (neuroendocrine markers), and CK20 (gastrointestinal marker). The gene discussed is TTF1; the disease is adenocarcinoma.