Hepatocellular adenoma (HCA) is a rare benign hepatocellular tumour developed in an otherwise healthy liver. The two main complications are bleeding from the HCA or malignant transformation to hepatocellular carcinoma (HCC). Risk factors for HCC include gender (men), size (> 8 cm) and subtype. Based on new molecular genetic analyses this review describes a new classification of adenomas using both genotype and phenotype. We want to provide an update on adenomas and give updated recommendations for diagnosis and treatment.