Hepatoid carcinoma of the pancreas.

BACKGROUND: The majority of primary extrahepatic neoplasms exhibiting features of hepatocellular carcinoma in terms of morphology, immunohistochemistry, and behavior have been described in the stomach. To the authors' knowledge only a few cases have involved other organ sites. They frequently are associated with other histologic type tumors such as adenocarcinoma, and portend an aggressive behavior. METHODS: Two examples of hepatoid carcinoma arising from the pancreas are reported in the current study. RESULTS: One case was a malignant islet cell tumor with a full-blown clinical syndrome of glucagon overproduction, histologic evidence of hepatocytic differentiation, bile production, and alpha-fetoprotein (AFP) positivity. The second tumor was a ductal carcinoma showing periodic acid-Schiff positive and diastase-resistant hyaline globules, AFP production, and ultrastructural resemblance to hepatocytic cells. CONCLUSIONS: The rare observation of cellular phenotypic transformation that corresponds with the process of hepatocytic transdifferentiation of pancreatic cells demonstrated in animal models and the common embryologic foregut derivation of the pancreas and liver also may explain the phenomenon of pancreatic hepatoid carcinoma.