From the Guidelines
The initial workup for a suspected carcinoid tumor should include imaging studies such as CT and MRI scans, biochemical evaluation with 24-hour urine collection for 5-HIAA, and potentially endoscopic procedures like colonoscopy, endoscopic ultrasound, or bronchoscopy, as recommended by the most recent guidelines 1. The workup process begins with assessing disease burden and possible primary location using imaging studies.
- CT scans of the abdomen and pelvis with contrast are typically used, followed by MRI if needed for better soft tissue visualization.
- For suspected bronchial carcinoids, chest CT is indicated.
- Multiphase CT or MRI scans should be used for evaluation of liver metastasis, as carcinoid tumors can appear isodense with liver on conventional CT scan, depending on contrast phase.
- Biochemical evaluation can also be helpful, particularly in patients with symptoms suggestive of hormone hypersecretion, and should include 24-hour urine collection for 5-HIAA 1.
- Additional recommendations vary by disease site and may include:
- Colonoscopy and small bowel imaging for jejunal, ileal, and colonic NETs
- Endoscopic ultrasound (EUS) and/or esophagogastroduodenoscopy (EGD) for duodenal and gastric NETs
- Proctoscopic examination for rectal NETs
- Bronchoscopy for bronchopulmonary and thymic NETs
- Functional imaging with radiolabeled somatostatin receptor scintigraphy, such as [111In-DTPA]-octreotide, may also be used in the initial evaluation of patients with carcinoid tumor 1.
From the Research
Initial Workup for Suspected Carcinoid Tumor
The initial workup for a suspected carcinoid tumor involves several diagnostic tests, including:
- Biochemical investigations to measure the levels of certain substances in the blood or urine
- Imaging studies to localize the tumor
- Other tests to assess the extent of the disease
Biochemical Investigations
Biochemical investigations play a crucial role in the diagnosis of carcinoid tumors. The following tests are commonly used:
- Measurement of 5-hydroxyindoleacetic acid (5-HIAA) in 24-hour urine collections 2, 3, 4
- Fasting plasma 5-HIAA assay, which has been shown to be a convenient and reliable alternative to 24-hour urine collections 2, 3
- Whole blood serotonin concentration, although this test has limitations due to saturation in platelets 2, 5
- Serum chromogranin A, a nonspecific biochemical tumor marker for carcinoid tumors 4
Imaging Studies
Imaging studies are essential for localizing the tumor and assessing the extent of the disease. The following imaging modalities may be used:
- Transabdominal ultrasonography (US) 4
- Endoscopy 4
- Endoscopic US 4
- Videocapsule endoscopy 4
- Computerized tomography (CT) 4
- Magnetic resonance imaging (MRI) 4
- Selective abdominal angiography 4
- 111In-pentetreotide scintigraphy (and intraoperative radionuclide probe) 4
- 123I (131I)-metaiodobenzylguanidine (MIBG) scintigraphy 4
- Bone scintigraphy 4
- 11C-5-HT positron emission tomography (PET) 4
Other Tests
Other tests may be used to assess the extent of the disease, including: