Which markers comprise the IHC panel for primary pancreatic adenocarcinoma?

• A. CA 19-9, CK7, CK20
• B. CA 19-9, CK7
• C. CK7, CK20, GATA3
• D. CA 19-9, CK7, CK20, CK5/6

Answer: (A)

Immunohistochemical profiling of pancreatic adenocarcinoma relies on detecting a pancreatic-associated marker alongside a CK7/CK20 pattern that helps distinguish it from other GI primaries. CA 19-9 is a marker often elevated in pancreatic cancer and, when shown in tissue by IHC, supports a pancreatic origin. The CK7/CK20 combination provides essential lineage information: pancreatic adenocarcinomas are typically CK7 positive and CK20 negative or variably positive, which helps separate them from colorectal cancers (usually CK20-positive, CK7-negative). Including CA 19-9 with CK7 and CK20 best fits the expected pancreatic phenotype and strengthens the diagnostic interpretation. In contrast, adding CK5/6 (a basal/squamous marker) or GATA3 (a marker for breast/urothelial lineage) would not align with the pancreatic profile and could mislead the diagnosis.