A Carcinoid tumors and carcinoid syndrome
Definition
Carcinoid tumors consist of slow-growing malignancies composed of enterochromaffin cells usually found in the gastrointestinal tract. They may also occur in the lung, pancreas, thymus, and liver. Carcinoid tumors have a low incidence rate of 1.9 per 100,000.
Pathophysiology
Speculation is that the advent and increasing use of proton pump inhibitors is a major contributory factor to the development of carcinoid tumors. A delay of several years frequently occurs before a diagnosis of carcinoid tumor is made. The gastrointestinal tract accounts for about two-thirds of carcinoids. Within the gastrointestinal tract, most tumors occur in the small intestine (41.8%), rectum (27.4%), and stomach (8.7%). Distant metastases may be evident at the time of diagnosis in 12.9% of patients, but better diagnostic techniques have contributed to improved survival rates.
The tumors can secrete several biologically active substances, including serotonin (5-hydroxytryptamine), kallikrein, histamine, prostaglandins, adrenocorticotropic hormone, gastrin, calcitonin, and growth hormone, among others. Approximately 5% to 10% of patients with carcinoid tumors develop carcinoid syndrome.
Clinical manifestations
The manifestations of carcinoid syndrome are in the table on pg. 100 and as follows:
