Ongoing research on the biology of these tumors may reveal new mechanisms for tumor development. Diagnosis
With a certain degree of clinical suspicion, the most useful initial test is the 24-hour urine levels of 5-HIAA (5-hydroxyindoleacetic acid), the end product of serotonin metabolism. Patients with carcinoid syndrome usually excrete more than 25 mg of 5-HIAA per day. Imaging
For localization of both primary lesions and metastasis, the initial imaging method is Octreoscan, where indium-111 labelled somatostatin analogues (octreotide) are used in scintigraphy for detecting tumors expressing somatostatin receptors. Median detection rates with octreoscan are about 89%, in contrast to other imaging techniques such as CT scan and MRI with detection rates of about 80%. Gallium-68 labelled somatostatin analogues such as 68Ga-DOTA-Octreotate (DOTATATE), performed on a PET/CT scanner is superior to conventional Octreoscan. Usually, on a CT scan, a spider-like/crab-like change is visible in the mesentery due to the fibrosis from the release of serotonin. 18F-FDG PET/CT, which evaluate for increased metabolism of glucose, may also aid in localizing the carcinoid lesion or evaluating for metastases. Chromogranin A and platelets serotonin are increased.Transthoracic echocardiogram shows valve thickening and reduction in mobility of the valves. Cardiac MRI is useful in showing ventricular anatomy and function. Localization of tumour
Tumour localization may be extremely difficult. Barium swallow and follow-up examination of the intestine may occasionally show the tumor. Capsule video endoscopy has recently been used to localize the tumor. Often laparotomy is the definitive way to localize the tumour. Another form of localizing a tumor is the octreoscan.
See also
Carcinoid
Neuroendocrine tumor
Small intestine neuroendocrine tumor
Kulchitsky cells
Apudoma
Serotonin Syndrome

References
Further reading


== External links ==