Hepatocellular adenomas in the Turkish population: reclassification according to updated World Health Organization criteria.

AIMS Hepatocellular adenoma is an uncommon liver neoplasm and the studies of HCA subtypes have been primarily limited to France, United States and Japan. We aimed to describe the clinicopathologic features of hepatocellular adenoma subtypes in Turkey. METHODS AND RESULTS The resection specimens of 59 cases diagnosed as "hepatocellular adenoma" collected from 15 institutions were reviewed to confirm the diagnosis and classify according to the current WHO 2019 classification. Glutamine synthetase, Liver-fatty acid binding protein, C-reactive protein, β-catenin and reticulin stains were performed. Of the 59 cases, 48 (81%) were diagnosed as hepatocellular adenoma. We identified 24 (50%) HNF1α-inactivated adenomas, 5 (10%) inflammatory adenomas, 15 (32%) β-catenin activated adenomas, 3 (6%) β-catenin activated inflammatory adenomas and 1 (2%) unclassified adenoma. Hepatocellular adenoma patients were predominantly female (F:M=5:1) with a median age of 34 and a median tumor diameter of 6 cm. In the β-catenin activated adenoma group nine cases (19%) showed cytoarchitectural atypia which also were referred to as atypical hepatocellular neoplasms. Three cases (6%) displayed focal areas supportive of transition to hepatocellular carcinoma in the β-catenin activated adenoma group. The original diagnosis of hepatocellular adenoma was changed to well-differentiated hepatocellular carcinoma in 9 cases and to focal nodular hyperplasia in 2 cases. CONCLUSION The major adenoma subtype is HNF1α-inactivated adenoma in our series. We found a low incidence of inflammatory type hepatocellular adenoma. Our data also showed β-catenin activated hepatocellular neoplasms including cases with atypical histology constitutes a relatively high portion of the cases. These findings are in contrast to most other studies of hepatocellular adenoma subtypes.