Neuroendocrine markers (synaptophysin and chromogranin) and mesothelial markers (WT-1 and calretinin) demonstrated 100% diagnostic performance metrics in their respective categories.<h4>Conclusion</h4>A morphology-guided IHC approach using a limited panel of markers, including TTF-1 and Napsin-A for adenocarcinoma and p40 with or without p63 for squamous cell carcinoma, demonstrated high diagnostic accuracy in the subclassification of lung carcinomas on biopsy specimens. The gene discussed is TTF1; the disease is lung carcinoma.