Jacubowski, Maureen A

Abstract Objective β-Catenin–mutated hepatocellular adenomas (HCAs) carry an increased malignant transformation risk and are screened by interpreting glutamine synthetase (GS) and β-catenin by immunohistochemistry (IHC). Our study aims to assess GS and β-catenin interpretation guidelines for applicability and reproducibility in predicting high-risk HCA and other relevant molecular alterations. Methods Hematoxylin and eosin (H&E), β-catenin, GS, and CD34 stains from 75 HCAs were interpreted by three pathologists using Method A (GS interpretation: negative, perivenular patchy, map-like, diffuse, and indeterminate) and Method B criteria (similar GS interpretation scheme based on a recent publication, with and without CD34 expression patterns). Ease of application and interpretation confidence level were assessed. High-risk IHC was defined as nuclear β-catenin and/or diffuse homogeneous GS. Molecular testing was performed on a subset of HCAs and controls. Results There were 57 resections and 18 biopsy specimens examined. Methods A and B (GS only) were rated as easy to apply, with high interpretation confidence (≥90% using both methods). Consensus rate was comparable in biopsy specimens (100% for both methods) and resections (88% for Method A, 93% for Method B). While the same cases were stratified into high-risk GS categories using both systems, clinically significant genetic alterations (TERT promoter, EGFR, MTOR, and TP53) were identified in 25% of cases stratified as not high risk by IHC. Conclusions Both methods have a similar ease of application and level of interpretation confidence, and they also detected β-catenin mutations as expected. Other relevant molecular alterations associated with risk of neoplastic progression and/or bleeding were detected in 25% of HCAs with the non-high-risk IHC phenotype, suggesting the value of molecular testing in this subset.