A patient’s liver FNA shows CA19-9+, CK7+, CK20+. Which carcinoma is most likely?

• A. Cholangiocarcinoma
• B. Hepatocellular carcinoma
• C. Small cell carcinoma
• D. Colon adenocarcinoma

Answer: (A)

The main idea here is using immunohistochemical markers to pin down where a liver lesion is coming from. CA19-9 is a tumor marker that’s especially elevated in cancers of the biliary tract, such as cholangiocarcinoma. CK7 is a cytokeratin typical of biliary epithelium and is commonly positive in cholangiocarcinoma, while CK20 is more often seen with colorectal cancers, where CK7 is usually negative. So when you have CA19-9 positive together with CK7 positivity, the pattern points toward a biliary origin. Hepatocellular carcinoma usually shows a different profile (often CK7-negative and CK20-negative with other markers), and colorectal cancer would more typically be CK20-positive and CK7-negative. The combination given best fits cholangiocarcinoma.