鹿毛 政義¹, 相島 慎一², 草野 弘宣³, 矢野 博久³

Masayoshi KAGE¹, Shinichi AISHIMA², Hironori KUSANO³, Hirohisa YANO³

¹純真学園大学保健医療学部医療工学科, ²佐賀大学医学部病因病態科学, ³久留米大学医学部病理学講座

¹Department of Medical Engineering, Junshin Gakuen University, ²Department of Pathology and Microbiology, Faculty of Medicine, Saga University, ³Department of Pathology, School of Medicine, Kurume University

キーワード : Nonalcoholic fatty liver, Nonalcoholic steatohepatitis, Liver pathology

非アルコール性脂肪肝疾患（nonalcoholic fatty liver disease: NAFLD）とは臨床所見に加え病理学的形態学の概念に基づくもので，大きく非アルコール性脂肪肝（nonalcoholic fatty liver: NAFL）と非アルコール性脂肪性肝炎（nonalcoholic steatohepatitis: NASH）に分類される．NASHは肝硬変や肝細胞癌へと進行する可能性があるので，NAFLとNASHの鑑別診断は重要である．NAFLは肝細胞の傷害を伴わない単純な脂肪肝であるが，NASHは主に小葉中心帯領域（ゾーン3）に分布する大滴性脂肪変性，炎症，風船様肝細胞が特徴である．肝生検はNAFLDを診断する上で有用な検査であるが侵襲的である．ゆえに，診断画像法を含むさまざまな非侵襲性手法が近年開発されている．NAFLDにおける画像診断の有用性を検証するためには，画像診断と組織病理学的所見は密接に関連しているので，病理組織所見が画像所見にどのように反映されているのかを明らかにする必要がある．ここでは，NAFLDの主な病理学的所見，すなわち肝細胞の脂肪変性，炎症，風船様肝細胞，Mallory-Denk体，線維化について概説し，肝硬変への進行過程についても説明を加えた．

Nonalcoholic fatty liver disease (NAFLD) is based on the concept of pathological morphology as well as clinical findings, and is broadly categorized into nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH). The differential diagnosis between NAFL and NASH is important because NASH has the potential to progress to cirrhosis and hepatocellular carcinoma. NAFL is simple hepatic steatosis without hepatocellular injury, while NASH is characterized by macrovesicular steatosis, inflammation, and ballooning hepatocytes with a predominantly centrilobular (zone 3) distribution. Liver biopsy is a useful test for diagnosing NAFLD, but it is invasive. Therefore, various noninvasive methods including diagnostic imaging have been developed in recent years. To verify their usefulness, it is necessary to clarify in detail how the pathological findings are reflected in the image findings as imaging and histopathological findings are closely related. We describe the main histological features of NAFLD, i.e., steatosis, inflammation, ballooning hepatocytes, Mallory-Denk bodies, and fibrosis, as well as the evolutional process to liver cirrhosis.