The diagnostic IHC profile (CK7+/CK20-) exhibited 86.7% specificity for pulmonary origin in our institutional cohort (2018–2023, n = 47), consistent with literature reports that > 80% of lung-derived adenocarcinomas demonstrate this pattern.[10] Notably, the combination of NapsinA and TTF-1 immunopositivity provided superior discriminatory capacity (sensitivity 92.1%, specificity 94.3%) for identifying pulmonary-derived metastases,[11] as confirmed in this case’s liver biopsy specimens. The gene discussed is TTF1; the disease is adenocarcinoma.