Contrast-Enhanced Ultrasound and Somatostatin Receptor Scintigraphy Unveil an Occult Neuroendocrine Tumor With Carcinoid Syndrome and Presumed Small Intestinal Origin - A Case Report.

A 68-year-old man with postprandial flushing and palpitations was referred for multiple hepatic lesions. Computed tomography showed hypoattenuating metastases without a detectable primary, whereas contrast-enhanced ultrasound revealed arterial hyperenhancement and Kupffer-phase defects, indicating hypervascularity typical of neuroendocrine tumors (NETs). Urinary 5-hydroxyindoleacetic acid elevation, together with liver biopsy findings, confirmed a well-differentiated NET (grade 2), presenting with carcinoid syndrome. Somatostatin receptor scintigraphy demonstrated diffuse hepatic uptake and a mesenteric focus, suggesting a small intestine origin. Lanreotide was initiated, achieving partial symptom improvement and radiologic stability. This case highlights contrast-enhanced ultrasound for demonstrating hypervascularity and somatostatin receptor scintigraphy for localizing an occult origin in NET.