Rapid advances in molecular and anatomic pathology have greatly improved our understanding of hepatocellular adenomas. Principle among them is a clinically relevant, histology-based classification that identifies hepatic adenomas at greatest risk for malignant transformation. This new classification system has led to general consensus on the major subtypes of hepatic adenomas. However, controversy remains regarding how to incorporate less common types of hepatic adenomas into the classification system and how to incorporate adenoma subtyping into clinical care. This article provides an in-depth review of how adenomas are classified, with a focus on the current rationale, the consensus, and controversies.