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Carcinoid - Diagnosis
Medical expert of the article
Last reviewed: 04.07.2025
Laboratory tests in the vast majority of cases confirm an increased content of 5-hydroxytryptamine in the blood and 5-hydroxyindoleacetic acid in the urine, with the excretion of the latter in the amount of 12 mg/day being suspicious, and over 100 mg/day being considered a reliable sign of carcinoid. It should be taken into account that reserpine, phenathiazine, Lugol's solution and other medications, as well as eating large amounts of bananas and ripe tomatoes, increase the content of serotonin in the blood and the end product of its metabolism - 5-hydroxyindoleacetic acid in the urine, while chlorpromazine, antihistamines and other medications decrease it. Therefore, when conducting laboratory tests, one should keep in mind these possible effects on the test results.
The diagnosis is confirmed by the results of histological examination of biopsy specimens. When stained with hematoxylin and eosin, small polygonal or round cells with basophilic nuclei are revealed. The cells are grouped into rosettes, nests and give an argyrophilic reaction with special staining.
The tumor is difficult to detect on X-ray examination due to its small size and eccentric growth.
Liver metastases of the tumor are easily recognized using ultrasound and computed tomography of the liver. Carcinoid is a malignant tumor, but it grows slowly and metastasizes late. The most typical metastases are in regional lymph nodes, liver, and metastasis to the cervical lymph nodes, lungs, brain, bones, and ovaries is possible.
Increased blood serotonin levels and increased urinary excretion of its metabolite 5-hydroxyindoleacetic acid (5-HIAA) - these indicators are especially sharply increased during an attack of hot flashes. Before the study, it is necessary to stop taking medications for 3 days (especially reserpine - it increases the serotonin content in the blood; phenothiazine compounds; diuretics) and exclude from the diet foods containing serotonin and tryptophan (bananas, pineapples, walnuts, avocados, plums, currants, tomatoes, eggplants, cheddar cheese). The upper level of normal urinary excretion of 5-HIAA is 10 mg / day. Urinary excretion of 5-HIAA 10-25 mg / day allows us to suspect the presence of carcinoid, and a value of more than 25 mg / day undoubtedly indicates the existence of carcinoid. If the results are inconclusive, a reserpine test is performed. Reserpine promotes the release of serotonin from brain cells and peripheral depots and prevents serotonin binding in platelets. In healthy people, after taking reserpine, the excretion of 5-HIAA in urine increases only in the first hours after taking reserpine, and in carcinoid syndrome it increases significantly compared to the initial level and remains elevated for several hours and even days.
In some cases, it is possible to detect the presence of intestinal carcinoid using colonoscopy (if localized in the large intestine), jejunoscopy (if localized in the jejunum), intestinal X-ray, and magnetic resonance imaging.
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