Uncommon Origin, Common Presentation: A Rare Case of Mesenteric Carcinoid Tumor Mimicking Functional Gastrointestinal Disorders.

Carcinoid tumors, a subtype of well-differentiated neuroendocrine neoplasms, are frequently misdiagnosed due to their indolent course and nonspecific gastrointestinal (GI) symptoms that mimic more common disorders. Here we report a rare case of a 59-year-old woman with hepatitis C and a history of intravenous drug use who presented with progressive abdominal pain, nausea, vomiting, diarrhea, and weight loss. Initial evaluations were inconclusive, but further imaging revealed a central mesenteric mass-an uncommon primary site-along with hepatic lesions, raising concern for metastatic disease. Elevated chromogranin A and biopsy confirmed a grade 1 neuroendocrine tumor. This case highlights the importance of considering carcinoid tumors in patients with persistent GI symptoms and emphasizes early recognition, particularly in atypical presentations, to guide timely and effective management.