TAC1 and neuroendocrine neoplasm: Because of the secretion of neurotransmitters, including serotonin, neurokinin A, and histamine, patients with small intestine neuroendocrine tumors may present with symptoms consistent with carcinoid syndrome such as flushing, diarrhea, valvular heart disease, and bronchospasms.27,28 However, as most patients report nonspecific abdominal pain or are asymptomatic, small intestine neuroendocrine tumors are often incidental findings on routine colonoscopy.24,26 Approximately 30% of patients will be metastatic at presentation, often to the liver.24,29