Overview
Carcinoid syndrome is a symptom complex observed in potentially malignant slow-growing neuroendocrine tumors that can occur in almost any organ. In 39% of cases, neoplasms that provoke carcinoid syndrome are localized in the small intestine, in 26% - in the appendix, in 15% - in the rectum, in 1-5% - in other parts of the large intestine, in 2-4% - in the stomach. , 2-3% - in the pancreas, 1% - in the liver and 10% - in the bronchi. In 20% of cases, carcinoid tumors of the gastrointestinal tract are combined with other neoplasms of the large intestine.
They are observed at any age, however, the average age of patients with this pathology is 50-60 years. Occasionally develop in childhood and adolescence. Men and women get sick equally often.
Carcinoids grow slowly. In the case of localization in the small intestine, they give metastases in 30-75%, in the large intestine - in 70% of cases. Carcinoids of the appendix metastasize very rarely, in contrast to its other localizations. Most often, carcinoid metastases are described in regional lymph nodes, the peritoneum, various parts of the intestine and the liver.
The tumor is usually located in the submucosal layer of the intestine and grows in the direction of the muscular and serous layers. Its dimensions are small (diameter often ranges from a few millimeters to 3 cm). When dissected, the tumor tissue has a yellow or gray-yellow color, is characterized by a high content of cholesterol and other lipids.
Against the background of carcinoid, thickening and shortening of the cusps of the tricuspid valve and the pulmonary artery valve often occur and, as a result, valve insufficiency, muscle hypertrophy and dilatation of the right ventricle.
The etiology of carcinoid:
Like many other tumors, is unknown. Many symptoms of the disease are caused by the hormonal activity of the tumor. A significant release of serotonin (5-hydroxytryptamine) - a product of the conversion of the amino acid tryptophan, by enterochromaffin tumor cells has been proven. Against the background of carcinoid, the content in the urine of the end product of the conversion of serotonin 5-hydroxyindoleacetic acid is sharply increased and in most cases is 50-500 mg (the norm is 2-10 mg).
The physiological activity of serotonin is manifested when it is in the blood in a free state. Tumor releases of serotonin explain a complex set of body reactions that are observed during carcinoid (serotonin) attacks.
In recent years, it has been proven that the carcinoid produces other biologically active substances (lysylbradykinin and bradykinin, histamine, prostaglandin, polypeptide-p), that is, it is a multihormonal tumor.
Carcinoid syndrome is not seen in all carcinoid tumour patients. This condition generally appears only after metastases in the liver manifest in carcinoids of the small and large intestine. This is because hormones from the gut enter the liver via the portal vein system and are subsequently degraded by liver enzymes. When a tumour spreads to the liver, the products of tumour metabolism begin to reach the general circulation straight through the hepatic veins, without being cleaved in the liver cells.