S5939 Unclassified Hepatic Adenoma in the Setting of Hepatic Adenomatosis: A Case Report With Molecular Characterization

Introduction: Hepatic adenomatosis was first described by Flejou et al. in 1985 as the presence of 10 or more hepatocellular adenomas (HCAs) in otherwise normal liver parenchyma. HCAs are benign epithelial liver tumors that can be subclassified into 4 major subtypes: hepatocyte nuclear factor-1α (HNF-1α) inactivated, β-catenin activated, inflammatory, and unclassified. Although typically benign, HCAs carry a risk of hemorrhage and malignant transformation into hepatocellular carcinoma (HCC), particularly in certain subtypes or when lesions are large or multifocal. Case Description/Methods: A 24-year-old woman with a history of class III obesity, Ehlers-Danlos syndrome, systemic lupus erythematosus, eosinophilic esophagitis, asthma, irritable bowel syndrome, on oral contraception presented with chronic abdominal pain, diarrhea, and episodes of jaundice. Laboratory evaluation was unremarkable. MRI of the abdomen revealed 13 bilobar hepatic lesions suggestive of HCAs - the largest was 4.2 × 3.7 cm in segment VI, which subsequently underwent biopsy and microwave ablation. Histopathologic analysis revealed a well-differentiated hepatocellular neoplasm with unpaired arterioles, mild cytologic atypia, patchy hepatocyte crowding, and focal sinusoidal dilatation. Immunohistochemistry demonstrated negative membranous β-catenin staining and pericentral glutamine synthetase staining, ruling out β-catenin–activated HCA and focal nodular hyperplasia. Serum amyloid A and C-reactive protein were negative, inconsistent with inflammatory HCA. Liver fatty acid-binding protein (LFABP) staining was retained, excluding HNF-1α-inactivated HCA and HCC. Although focal reticulin abnormalities were noted, the findings were most consistent with an unclassified HCA. Following ablation, the patient’s symptoms improved. She has since repeated surveillance imaging every 6 months. Her most recent MRI showed stable adenomas without evidence of new lesions. Discussion: This case is notable for a young woman with class III obesity and overlapping autoimmune conditions. Although obesity is a known risk factor for inflammatory HCA, immunohistochemistry did not support this subtype nor HNF1A-inactivated or β-catenin–activated, instead favoring an unclassified phenotype. This case highlights the need for molecular subtyping and individualized care in hepatic adenomatosis, particularly in patients with atypical or overlapping risk factors.