Negative staining for cytokeratin 7 (CK7), cytokeratin 20 (CK20), caudal-type homeobox transcription factor 2 (CDX2), and thyroid transcription factor 1 (TTF-1) helped exclude primary gastric, gastrointestinal, and pulmonary neoplasms. The gene discussed is KRT20; the disease is lung neoplasm.