BackgroundHepatocellular adenoma (HCA) is an uncommon solid, solitary, benign liver lesion that develops in an otherwise normal-appearing liver. Hemorrhage and malignant transformation are the most important complications. Risk factors for malignant transformation include advanced age, male gender, use of anabolic steroids, metabolic syndrome, larger lesions, and beta-catenin activation subtype. The identification of higher risk adenomas enables the selection of patients most suitable for aggressive treatment and those who benefit with surveillance, minimizing the risks for these predominantly young patients.Case Presentation. We present the case of a 29-year-old woman with a history of oral contraceptive intake for 13 years, which was sent to evaluation in our Hepato-Bilio-Pancreatic and Splenic Unit because of a large nodular lesion in segment 5 of the liver, compatible with HCA, and was proposed to surgical resection. Histological and immunohistochemical investigation revealed an area with atypical characteristics, suggesting malignant transformation.ConclusionsHCAs share similar imaging characteristics and histopathological features with hepatocellular carcinomas; therefore, immunohistochemical and genetic studies assumes great importance to discriminate adenomas with malignant transformation. Beta-catenin, glutamine synthetase, glypican-3, and heat-shock protein 70 are promising markers to identify higher risk adenomas.