Coexisting focal nodular hyperplasia and diffuse hepatic metastases from an ileal neuroendocrine tumor: a case report and literature review.

Introduction and importance: Focal nodular hyperplasia (FNH) is a benign liver lesion usually associated with vascular abnormalities. Neuroendocrine tumors (NETs), on the other hand, frequently metastasize to the liver and typically appear as hypervascular lesions. The coexistence of FNH and diffuse hepatic metastases from an ileal NET is exceptionally rare and represents a major diagnostic challenge because both entities may present as hypervascular liver lesions, potentially leading to misdiagnosis and inappropriate management. Case presentation: A 56-year-old woman with a history of epilepsy treated with sodium valproate presented with progressive right upper quadrant pain and abdominal distension. Imaging showed a large hepatic lesion suggestive of FNH along with multiple hypervascular liver nodules suspicious for metastases. A CT-guided liver biopsy demonstrated metastatic well-differentiated NET with a Ki-67 index below 2%. Laboratory tests revealed elevated chromogranin A and urinary 5-hydroxyindoleacetic acid levels. The patient also had chronic diarrhea and moderate tricuspid regurgitation consistent with carcinoid syndrome. A ^68 Ga-DOTANOC positron emission tomography/computed tomography localized the primary tumor to the ileum. The integration of radiological, functional, and histopathological findings enabled accurate diagnosis and appropriate therapeutic planning. Surgical resection of the primary tumor was performed, followed by long-acting octreotide therapy. The patient remained clinically stable, with no progression of the hepatic lesions during follow-up. Clinical discussion: The presence of multiple hypervascular liver lesions in patients with NETs raises important diagnostic issues, especially when benign and malignant lesions coexist. This case demonstrates the value of integrating hepatobiliary magnetic resonance imaging (MRI), histopathological confirmation, and functional imaging to accurately distinguish FNH from metastatic disease and to guide appropriate therapeutic management. Conclusion: The coexistence of FNH and diffuse liver metastases from an ileal NET is rare. This case highlights the pivotal role of a multimodal diagnostic approach combining hepatobiliary MRI, functional imaging, and targeted histopathological confirmation to distinguish benign from malignant hypervascular liver lesions, avoid diagnostic pitfalls, and optimize patient management.