Preserved or enhanced OATP1B3 expression in hepatocellular adenoma subtypes with nuclear accumulation of β‐catenin

Aim Recent studies have indicated that hepatocellular adenoma ( HCA ) is a heterogenous group of benign tumors with various genetic and clinicopathological characteristics. We delineated the clinicopathological characteristics of HCA subtypes and evaluated the expression of transporter protein OATP 1 B 3 in HCA . Methods HCA in 34 J apanese patients were investigated immunohistochemically and classified into four subtypes ( HNF 1α‐inactivated type, H ‐ HCA ; β‐catenin‐activated type, b‐ HCA ; inflammatory type, I ‐ HCA ; unclassified type, u‐ HCA ). Immunostaining of OATP 1 B 3 protein in HCA tissue sections was performed to determine the association between OATP 1 B 3 expression and HCA subtypes. Results HCA was categorized into the following four subtypes and two combined subtypes: 10 H ‐ HCA (29%), 10 I ‐ HCA (29%), seven b‐ HCA (21%), two b‐ HCA / H ‐ HCA (6%), two b‐ HCA / I ‐ HCA (6%) and three u‐ HCA (9%). The male‐to‐female ratio was 18:16. Oral contraceptive use was rare but seven HCA were found in patients with glycogen storage disease, congenital absence of the portal vein and idiopathic portal hypertension. OATP 1 B 3 expression was decreased in 24 HCA but was preserved or increased in 10 HCA . All nine HCA with nuclear staining for β‐catenin showed preserved or enhanced OATP 1 B 3 expression, indicating a significant association between nuclear β‐catenin accumulation and OATP 1 B 3 expression in HCA . Conclusion HCA subtype classification was validated in 91% of our J apanese subjects although their clinical backgrounds including rare contraceptive use were different from E uropean subjects. A close association between preserved or enhanced OATP 1 B 3 expression and b‐ HCA subtype indicated important modalities for clinical decisions in the treatment and follow up of patients with HCA .