Carcinoid was first described at the end of the 19th century. In the 50s of the last century, a group of researchers led by Waldenstr�m compiled an extensive description of the histological and histochemical features of carcinoid tumors, and also proved the connection between such neoplasms and the development of carcinoid syndrome. For a long time, carcinoids were considered benign tumors, but research in recent years has shaken this point of view. It was found that, despite their slow growth, the formations have certain signs of malignancy and can metastasize to distant organs. Treatment of carcinoid syndrome is carried out by doctors working in the field of oncology, endocrinology, gastroenterology, cardiology, general surgery and other specialties.
The cause of the development of carcinoid syndrome is the hormonal activity of tumors originating from the neuroendocrine cells of the APUD system. Symptoms are determined by changes in the levels of various hormones in the patient's blood. Typically, such neoplasms secrete large amounts of serotonin. As a rule, there is an increase in the production of histamine and prostaglandins, bradykinin and polypeptide hormones.
Carcinoid syndrome does not occur in all patients with carcinoid tumors. In carcinoids of the small and large intestine, this syndrome usually develops only after the appearance of metastases in the liver. This is explained by the fact that hormones from the intestines with the blood enter the liver through the portal vein system, and are then destroyed by liver enzymes. Metastasis to the liver leads to the fact that the products of tumor metabolism begin to directly enter the general bloodstream through the hepatic veins, without being broken down in liver cells.
An increase in serotonin levels provokes diarrhea, abdominal pain, malabsorption and cardiac pathology. As a rule, with carcinoid syndrome, fibrous degeneration of the endocardium of the right half of the heart is observed. The left side of the heart is rarely affected because serotonin is destroyed as blood passes through the lungs. An increase in bradykinin and histamine causes hot flashes. The role of polypeptide hormones and prostaglandins in the development of carcinoid syndrome has not yet been clarified.
