Pathology of Hepatocellular Adenoma: Subtypes and Rare Morphologic Features

Abstract

ABSTRACT Background: The molecular classification has been divided HCA into four main subgroups: hepatocyte-nuclear-factor-1a mutated (H-HCA), B-catenin type (HA-B), inflammatory type (HA-I) and unclassified type. Those subgroups were linked with risk factors, clinical behavior, histological features, imaging and malignant transformation. Subtyping is useful to predict HA’s behavior and also to detect morphology which may have the potential to affect the prognosis. We aimed to review subtype features of our hepatocellular adenoma cases and discuss the importance of the rare morphologic features. Methods: Fifteen Hepatocellular adenoma cases (10 resections, 3 explants and 2 biopsies) were included in this study. Hematoxylin and eosin (H&E) stained slides, Reticulin and Masson’s trichrome stains, as well as immunohistochemical studies (IHC), were used to evaluate general morphologic and immunophenotypic features performed with B-catenin, SAA amyloid and Glutamine Synthetase(GS) using standard laboratory techniques in the Ventana Benchmark Ultra platform. CD34 immunohistochemical stains were performed on atypical cases to evaluate the presence of vascularization. Results: By morphologic features and Immunohistochemistry, 3 HA-B (%20), 4 HA-I (%26.6), 4 HA-H (%26.6) and 4 HA-U (%26.6) cases were classified. Two HA cases had Dubin-Johnson pigment and Two of the beta-catenin mutated HAs had bone marrow metaplasia. In one of the cases, malignant transformation in the HA was present. The microscopic findings included hemorrhage, pigment formation, granuloma formation, presence of inflammation, presence and degree of steatosis, preserved or non-preserved reticulin network. Conclusions: Besides the classic morphologic features; granuloma formation, pigmentation, bone marrow metaplasia can be seen in HAs. Although the prognostic significance of those is not known, they are considered to have a role in the development and progression of HA.