Table 18.1 Nomenclature of bone tumors
Fig. 27.11 Patient with metastatic carcinoid tumor during a flush.
Carcinoid tumor of the small bowel.
The production of 5-hydroxytryptamine (serotonin) is important for diagnosis. The 5-hydroxytryptamine level in the plasma is usually raised. However, it is simpler and more reliable to assess the 5-hydroxyindole acetic acid (5-HIAA) level in the urine over 24 hours. 5-HIAA is an end product of serotonin metabolism that is almost always highly elevated in patients with carcinoid syndrome.
• The carcinoid syndrome must be distinguished from idiopathic flushing (IF); patients with IF more often are females, younger, and with a longer duration of symptoms; palpitations, syncope, and hypotension occur primarily in patients with IF.
• The biochemical marker for carcinoid syndrome is increased 24-hours urinary 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of serotonin (5-hydroxytryptamine).
• False elevations can be seen with ingestion of certain foods (bananas, pineapples, eggplant, avocados, walnuts) and certain medications (acetaminophen, caffeine, guaifenesin, reserpine); therefore patients should be on a restricted diet and should avoid these medications when the test is ordered.
• Liver function studies are an unreliable indicator of liver involvement.
• Chest x-ray examination is useful to detect bronchial carcinoids.
• CT scans of abdomen or a liver and spleen radionuclide scan is useful to detect liver metastases (palpable in > 52% of cases).
• Iodine-123 labeled somatostatin (123-ISS) can detect carcinoid endocrine tumors with somatostatin receptors.
• Scanning with radiolabeled octreotide can visualize previously undetected or metastatic lesions.
Avoidance of ethanol ingestion (may precipitate flushing)
ACUTE GENERAL Rx
• Surgical resection of the tumor can be curative if the tumor is localized or palliative and result in prolonged asymptomatic periods if metastases are present. Surgical manipulation of the tumor can, however, cause severe vasomotor abnormalities and bronchospasm (carcinoid crisis).
• Percutaneous embolization and ligation of the hepatic artery can decrease the bulk of the tumor in the liver and provide palliative treatment of tumors with hepatic metastases.
• Cytotoxic chemotherapy: combination chemotherapy with 5-fluorouracil and streptozotocin can be used in patients with unresectable or recurrent carcinoid tumors; however, it has only limited success.
• Control of clinical manifestations:
1. Diarrhea usually responds to diphenoxylate with atropine (Lomotil).
2. Flushing can be controlled by the combination of H1 - and H2 -receptor antagonists (e.g., diphenhydramine 25 to 50 mg PO q6h and ranitidine 150 mg bid).
3. Somatostatin analog (SMS 201-995) is effective for both flushing and diarrhea in most patients.
4. Bronchospasm can be treated with aminophylline and/or albuterol.
• Nutritional support: supplemental niacin therapy may be useful to prevent pellagra, because the tumor uses dietary tryptophan for serotonin synthesis, resulting in a nutritional deficiency in some patients.
• Subcutaneous somatostatin analogues (octreotide 150 µg SC tid) have been used successfully for long-term control of symptoms in patients with unresectable neoplasms.
• Echocardiography and monitoring for right-sided CHF are recommended for patients with unresectable disease because endocardial fibrosis, involving predominantly the endocardium, chordae, and valves of the right side of the heart, can occur and result in right-sided CHF.
• Prognosis varies with the stage and location of the tumor.
• Carcinoids of the appendix and rectum have a low malignancy potential and rarely produce the clinical syndrome; metastases are also uncommon if the size of the primary lesion is < 2 cm in diameter.
• The carcinoid syndrome is caused by neoplasms originating from neuroendocrine cells.
• Carcinoid tumors are principally found in the following organs: appendix (43%), small bowel (22%; 15% in the ileum), rectum (18%), bronchi (14%), esophagus, stomach, colon (15%), ovary, biliary tract, pancreas (5%).
• Carcinoid tumors do not usually produce the syndrome unless liver metastases are present or the primary tumor does not involve the GI tract.