Liver-cell adenomas are benign lesions of the liver occurring predominantly in young women. Hepatocellular carcinomas in most of the cases arise in a cirrhotic liver during the fifth or sixth decade. We describe the case of a 40-year-old woman in whom work-up for epigastric pain revealed a peptic ulcer and a large hepatic mass. Tests for chronic liver diseases were negative. Imaging findings and biopsy specimens of the tumour were inconclusive. The tumour was surgically removed and a hepatocellular carcinoma arising within a liver-cell adenoma in a non-cirrhotic liver was found. Malignant transformation of liver-cell adenoma has only been reported in a few case reports. Mechanisms of transformation remain unclear. The imaging findings as well as histological features are presented in detail and the literature is discussed.