A tumor immunohistochemistry panel shows: CK7+, CK20−, TTF-1+, Napsin A+. Which primary malignancy does this pattern most consistently identify?
- A Lung adenocarcinoma ✓
- B Colonic adenocarcinoma
- C Pancreatic ductal adenocarcinoma
- D Urothelial carcinoma
Correct answer: A. Lung adenocarcinoma
Explanation
The CK7+/CK20− pattern combined with TTF-1 and Napsin A positivity is the classic immunoprofile of lung adenocarcinoma. TTF-1 is expressed in thyroid and lung epithelium, and Napsin A is highly specific for lung adenocarcinoma. Colonic adenocarcinoma is CK7−/CK20+; pancreatic ductal adenocarcinoma is typically CK7+/CK20+; and urothelial carcinoma is CK7+/CK20+ with GATA-3 positivity.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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