A 36-year-old man in otherwise good general condition and with completely normal laboratory results suffered from right upper abdominal pain. Hepatomegaly was diagnosed as due to cystic liver disease after ultrasound, computed tomography and magnetic resonance imaging. Recurrent abdominal pain continued over several months. Open liver biopsy eventually revealed trabecular-tubular carcinoma (APUDoma). Silver reaction was positive in many tumour cells. Electronmicroscopy demonstrated membrane-bound granules typical for endocrine cells. Immunohistological examinations of various hormones and of neurone-specific enolase were negative, but repeatedly measured high serum levels of pancreatic polypeptide and of beta-HCG nonetheless suggested an endocrine tumour. This case demonstrates that nonparasitic cystic changes in the liver, especially multiple ones, should have a firm diagnosis established by invasive means. Endocrine tumours can be mistaken for polycystic liver disease.