Introduction Carcinoid syndrome (CS) is a paraneoplastic syndrome frequently diagnosed in patients with neuroendocrine tumors (NETs) associated with the secretion of humoral factors. These factors include serotonin (5-HT), which appears to be the most common substance associated with the syndrome, as well as histamine, kallikrein, prostaglandins, and tachykinins. Among patients diagnosed with NETs located in the duodenum and small intestine, approximately 20% will develop CS during follow-up. The presence of CS is strongly associated with a higher tumor grade and […]