Grade 1 Hepatic Neuroendocrine Tumor with Peritoneal Metastases: Case Report - Diagnostic Reasoning and Management Challenges.

Introduction: Neuroendocrine tumors are rare neoplasms that commonly metastasize to the liver, while peritoneal metastases occur less frequently but are associated with poorer outcomes. This report presents a rare case of concurrent liver metastasis and peritoneal metastasis from a well-differentiated neuroendocrine tumor, emphasizing the diagnostic reasoning and multidisciplinary management involved. Case Presentation: A 62-year-old woman with a history of laparoscopic cholecystectomy was incidentally found to have multiple hypoechoic liver lesions and a mesenteric mass. Contrast-enhanced computed tomography and magnetic resonance imaging revealed hepatic and peritoneal nodules consistent with metastatic disease. Laparoscopic wedge resection of hepatic segments VI and VIII and biopsy of peritoneal implants confirmed a grade 1 neuroendocrine tumor positive for chromogranin A, synaptophysin, and INSM1, with a Ki-67 index of 2-3%. The patient underwent cytoreductive debulking surgery, achieving approximately 70% tumor reduction, followed by long-acting octreotide therapy. Postoperative recovery was uneventful, and follow-up imaging demonstrated no recurrence. Conclusion: This case report underscores the importance of early recognition and a multidisciplinary approach in managing indolent neuroendocrine tumors with multisite metastases. Combined surgical and medical strategies, including debulking surgery and octreotide therapy, can achieve durable disease control and favorable outcomes.