Pancreatic-polypeptide-producing apudoma of the liver.

A large hepatic excised from a 62-year-old man resembled a carcinoid tumor. No endocrine syndrome was present and an alternative primary source of tumor was found, despite an intensive search. The tumor cells were classified according to the type of electron-dense granules present: ACTH, gastrin (G), bombesin (P), and pancreatic polypeptide (PP) type granules were identified. Immunofluorescent staining with antibodies to several polypeptide hormones detected PP-containing tumor cells only. This rare tumor is therefore a PP-apudoma; possibly of intrahepatic bile duct origin.