Focal Nodular Hyperplasia Presenting With Biliary Obstruction and Intrahepatic Gallstones: A Case Report and Literature Review.

Focal nodular hyperplasia (FNH) is a benign liver lesion that is most often asymptomatic and does not require surgical intervention. Rarely, FNH may cause biliary obstruction and stasis, which can lead to intrahepatic gallstone (hepatolithiasis) formation. We describe a case of a 44-year-old female patient who was incidentally found to have biliary ductal dilation with an associated malignant-appearing 3.5 cm left liver mass. Workup included contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI). A biopsy was deferred, given the high clinical suspicion. An open anatomic left hepatectomy was performed without complications, and the patient recovered well. Pathology demonstrated a 3.5 cm FNH with extensive intrahepatic cholelithiasis but no malignancy. Despite high-quality preoperative imaging, FNH could not be distinguished from intrahepatic cholangiocarcinoma, underscoring the diagnostic challenge posed by atypically presenting benign hepatic lesions. Surgical resection was indicated, given the biliary obstruction, stone burden, and radiologic suspicion for malignancy, and was performed safely with favorable outcomes.