A 63-year-old male with a liver lesion; immunohistochemistry shows AFP and HepPar1 positivity. What is the most likely origin of this lesion?

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

Answer: (C)

Immunohistochemistry helps identify where a tumor comes from by detecting proteins typical of specific cell types. AFP is a protein produced by fetal liver and by many hepatocellular carcinomas, while HepPar1 stains hepatocytes and is commonly positive in hepatocellular carcinoma. When a liver lesion shows both AFP and HepPar1 positivity, it strongly indicates hepatocellular differentiation rather than a biliary or gastric origin. Cholangiocarcinoma, arising from bile ducts, would not characteristically express these hepatocyte markers; gastric adenocarcinoma would reflect gastric-type markers; small cell carcinoma shows neuroendocrine markers. So the pattern points to hepatocellular carcinoma originating from hepatocytes.