Which markers comprise the IHC panel for primary lung adenocarcinoma?

• A. Napsin A, TTF-1, Ber-Ep4, CK7
• B. Napsin A, TTF-1, CK7, CK20
• C. TTF-1, CK7, p63, CK5/6
• D. Napsin A, CK7, Ber-Ep4, CK20

Answer: (A)

The markers used to support a diagnosis of primary lung adenocarcinoma should point to lung origin and glandular/type adenocarcinoma while helping to exclude mesothelial tumors. Napsin A and TTF-1 are commonly expressed in lung adenocarcinomas and provide strong evidence of pulmonary origin. CK7 is a typical epithelial cytokeratin pattern seen in lung adenocarcinoma, reinforcing the glandular phenotype. Ber-EP4 helps distinguish adenocarcinoma from mesothelioma, since mesothelioma is often Ber-EP4 negative. Together, these four markers form a coherent panel that supports lung adenocarcinoma and helps rule out mesothelial disease.

Markers like CK20 or p63/CK5/6 either point toward non-lung origins (CK20) or toward squamous differentiation (p63, CK5/6), which are not ideal for confirming primary lung adenocarcinoma.