Pictures of focal nodular hyperplasia and hepatocellular adenomas

Abstract

This practical atlas aims to help liver and non liver pathologists to recognize benign hepatocellular nodules on resected specimen. Macroscopic and microscopic views together with immunohistochemical stains illustrate typical and atypical aspects of focal nodular hyperplasia and of hepatocellular adenoma, including hepatocellular adenomas subtypes with references to clinical and imaging data. Each step is important to make a correct diagnosis. The specimen including the nodule and the non-tumoral liver should be sliced, photographed and all different looking areas adequately sampled for paraffin inclusion. Routine histology includes HE, trichrome and cytokeratin 7. Immunohistochemistry includes glutamine synthase and according to the above results additional markers such as liver fatty acid binding protein, C reactive protein and beta catenin may be realized to differentiate focal nodular hyperplasia from hepatocellular adenoma subtypes. Clues for differential diagnosis and pitfalls are explained and illustrated.

Keywords: Focal nodular hyperplasia; Hepatocellular adenoma; Inflammatory hepatocellular adenoma; Beta catenin; Hepatocyte nuclear factor 1 alpha

Core tip: In this paper are illustrated macroscopic and microscopic aspects of focal nodular hyperplasia and hepatocellular adenoma. These illustrations represent typical as well as less usual aspects of these two benign hepatocellular tumors. Microscopic pictures are performed using classical routine stains such as HE, trichrome or cytokeratin 7 or less usual markers proven of great interest to identify focal nodular hyperplasia (FNH) such as glutamine synthase or liver fatty acid briding protein, C reactive protein or b catenin to identify hepatocyte nuclear factor 1 alpha mutated hepatocellular adenoma (HCA), inflammatory HCA, β-catenin mutated HCA respectively. These illustrations combined with brief clinical information should be helpful for pathologists for their practice. Indeed if FNH are rather frequent tumor easy to recognize, there are difficulties when key features are lacking or when features such as steatosis or sinusoidal dilatation, features of HCA, are present. The great message of this paper is the possibility to identify HCA subtypes, a key feature for the coming years to better manage patients.