Which panel is most helpful in identifying squamous cell carcinoma in the lung?

• A. Synaptophysin and Chromogranin
• B. TTF-1 and Napsin A
• C. p63/p40 and CK5/6
• D. Napsin A and p63

Answer: (C)

Immunoprofiling to distinguish lung cancers relies on lineage-specific markers. Squamous cell carcinoma in the lung shows squamous differentiation with markers like p40 (highly specific for squamous lineage) and CK5/6 (keratin pattern typical of squamous cells). The combination of p40 or p63 with CK5/6 is especially informative because it highlights squamous phenotype, making the diagnosis with strong confidence. By contrast, adenocarcinoma of the lung usually expresses TTF-1 and Napsin A, while neuroendocrine tumors express synaptophysin and chromogranin. So using a panel that includes squamous markers (p40/p63 and CK5/6) provides the clearest identification of squamous cell carcinoma in the lung.