Which marker is included in a Mesothelioma second-line IHC panel?

• A. Calretinin
• B. PanCK
• C. TTF-1
• D. CEA

Answer: (B)

In IHC practice, a second-line mesothelioma panel is used to confirm epithelial differentiation and to help distinguish mesothelioma from metastatic carcinomas. Pan cytokeratin stains most epithelial cells, including mesothelial cells, so it serves as a broad confirmation that the tumor is epithelial and that the stain worked. Because PanCK is positive in many epithelial tumors as well as mesothelioma, its role is not to distinguish between them by itself, but to provide a baseline epithelial profile that supports the interpretation of more specific markers. In this context, the second-line panel leverages PanCK alongside targeted markers to corroborate the epithelial nature of the lesion and to aid in the final differential diagnosis.