Which markers are shared by both the cholangiocarcinoma and pancreatic adenocarcinoma IHC panels?

• A. CA19-9, CK7, CK20
• B. CA19-9, CK7
• C. CK7, CK20
• D. CA19-9, CK20

Answer: (A)

Immunohistochemistry for pancreatobiliary tumors often shows a shared pattern, reflecting their common ductal origin. CA19-9 is a mucin-type antigen that is frequently positive in both pancreatic ductal adenocarcinoma and cholangiocarcinoma, making it a strong supporting marker for tumors of this region. CK7 is a cytokeratin expressed by biliary epithelium and pancreatic ducts, so most tumors arising from these sites are CK7 positive. CK20, while more variable, can also be seen in pancreatobiliary tumors, especially in cases with intestinal differentiation or overlapping phenotypes, so it can appear in both panels. Together, CA19-9, CK7, and CK20 form a commonly shared set of markers for these two cancers, which is why they appear on both IHC panels.