Introduction: Accurate subtyping of lung carcinomas on small biopsies is critical for targeted therapy selection; however, regional data on the diagnostic performance of immunohistochemical (IHC) markers remain limited. This study aimed to evaluate the histomorphological spectrum and diagnostic utility of a comprehensive IHC panel for lung carcinoma. Materials and methods: A retrospective analysis was conducted on 97 lung biopsy cases collected between January 2024 and December 2025 at a tertiary care center in Rajasthan, India. Formalin-fixed paraffin-embedded tissues were evaluated using hematoxylin and eosin (H&E) staining and IHC markers, including p40, p63, thyroid transcription factor-1 (TTF-1), Napsin-A, synaptophysin, chromogranin, WT-1, calretinin, and pancytokeratin. Tumors were subclassified based on combined morphologic and IHC findings. Results: Adenocarcinoma (56, 57.7%) and squamous cell carcinoma (33, 34.0%) were the predominant subtypes. Most patients were male (76, 78.4%) and in the 61-70 years age group (42, 43.3%). Bronchoscopy-guided biopsies (72, 74.2%) were the most common, with the right lower lobe as the most frequent site (31, 32.0%). For squamous cell carcinoma, p40 demonstrated an overall diagnostic accuracy of 96.7% with 100% specificity. For adenocarcinoma, TTF-1 showed 95.1% accuracy with 96.0% sensitivity, while Napsin-A showed 93.8% accuracy with 100% specificity. Neuroendocrine markers (synaptophysin and chromogranin) and mesothelial markers (WT-1 and calretinin) demonstrated 100% diagnostic performance metrics in their respective categories. Conclusion: 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. These findings are consistent with current WHO recommendations and support the practical utility of focused IHC panels in routine diagnostic practice. Such strategies may help achieve accurate tumor subtyping while facilitating efficient use of limited biopsy tissue.
Mantri et al. (Mon,) studied this question.