Duodenal NET with Synchronous Liver Metastases: A Case Report

Introduction Duodenal neuroendocrine tumors (NETs) are rare, comprising only 2–3% of gastrointestinal NETs, and often grow silently until distant metastasis occurs. Case description We present a 69-year-old previously healthy man who presented with two weeks of weight loss and abdominal pain, found to have a cholestatic pattern of liver dysfunction. Imaging revealed hepatomegaly with extensive heterogeneous liver lesions, and upper endoscopy found an ulcerative lesion at the duodenal bulb. Biopsies confirmed a well-differentiated duodenal NET Grade 3, with the liver metastasis graded as well-differentiated NET Grade 2. Owing to his advanced hepatic burden, marked liver dysfunction, and rapid clinical decline, he was considered unfit for systemic therapy and transitioned to palliative care. Discussion This case highlights the insidious course of duodenal NETs, the importance of distinguishing well-differentiated NET G3 from neuroendocrine carcinoma despite a shared Ki-67 above 20%, and the value of sampling multiple lesions given the grade discordance seen between the primary and its metastasis.