A 50-year-old man with a history of asbestos exposure presents with a pleural-based mass. Biopsy shows biphasic tumor with epithelioid and sarcomatoid components. The most useful IHC combination for diagnosing malignant mesothelioma versus metastatic adenocarcinoma is:
- A Vimentin+ alone differentiates mesothelioma from adenocarcinoma
- B CD45+ distinguishes mesothelioma from all carcinomas
- C Calretinin+, WT1+, CK5/6+, D2-40+ (mesothelioma) versus TTF-1+, CEA+, MOC-31+ (adenocarcinoma) ✓
- D EMA positivity confirms mesothelioma over adenocarcinoma
Correct answer: C. Calretinin+, WT1+, CK5/6+, D2-40+ (mesothelioma) versus TTF-1+, CEA+, MOC-31+ (adenocarcinoma)
Explanation
Malignant mesothelioma shows positivity for mesothelial markers: calretinin (nuclear and cytoplasmic), WT1 (nuclear), CK5/6, D2-40 (podoplanin), and mesothelin. Metastatic pulmonary adenocarcinoma is positive for TTF-1, CEA, MOC-31, and BerEP4. Using a panel with two positive mesothelioma markers and two negative adenocarcinoma markers (or vice versa) provides the best diagnostic accuracy. EMA is positive in both; vimentin is non-specific; CD45 is a leukocyte marker.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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