Pathological Diagnosis of Benign Hepatocellular Nodular Lesions Based on the New World Health Organization Classification

There are various types of benign hepatocellular nodular lesions, and their diagnostic criteria were formulated in detail. However, in 2010, the new World Health Organization (WHO) classification introduced immunohistochemical diagnostic criteria for hepatocellular adenoma (HCA) reflecting molecular pathological properties, and HCA was classified into 4 subtypes. These criteria were useful for its differential diagnosis from focal nodular hyperplasia (FNH). They were also useful for the diagnosis of HCA, its subtyping, and differentiation from FNH in Japan. However, the new WHO classification is based on principles that differ from those of conventional definitions of disease concepts and methods for the differential diagnosis. Therefore, it has caused disagreements in the diagnosis in some cases. Based on this background, we present a new perspective on the diagnosis of benign hepatocellular nodular lesions.