In a retrospective review of 245 poorly differentiated non–small cell lung cancers, TTF-1 and napsin A were both specific (87% vs 100%), but TTF was more sensitive than napsin A (80 vs 64%) for lung adenocarcinoma.24 In this case report, the patient had tumor that was TTF-1 and napsin A positive, yet negative for intestinal (CK20 and CDX2) and neural (chromogranin, synaptophysin, and CD56) biomarkers, supporting metastatic adenocarcinoma with an immunoprofile favoring pulmonary origin. This evidence concerns the gene CDX2 and neoplasm.