Carcinoid is a relatively rare tumor, which is based on cells with ability to produce hormones. Carcinoid often behaves as a benign tumor, but sometimes it may produce metastases. Because of this erratic behavior it belongs among semi-malignant tumors.
The tumor arises from hormonally active cells that are scattered in the digestive system. That is why the tumor location may be very variable. Carcinoid may occur in the wall of the stomach, small intestine and colon – it is especially frequent in the appendix. It can also grow outside the digestive tract, for example in lungs. The exact cause of the tumor occurrence is unknown; it is probably a combination of a certain genetic predisposition and some outer factors.
Carcinoid may be asymptomatic and it is often just an incidental finding during appendectomy. Clinical symptoms of carcinoid are related to production of various active substances by the tumor cells including serotonin, bradykinin, histamine, and many others. The manifestation is known as the carcinoid syndrome. The syndrome includes diarrhea, abdominal pain, weight loss, bouts of face flushing, shortness of breath, cough and palpitations. The symptoms have usually paroxysmal character with a sudden start and end. The symptoms sometimes occur without any provoking factor, other times they depend on alcohol consumption or eating food with a higher concentration of serotonin (bananas, pineapple, kiwi, etc.).
It is not easy to state the diagnosis as the tumor is quite rare. As mentioned above, it is often found randomly during a surgical intervention on the guts. The diagnostics can be done in a symptomatic form according to the clinical symptoms, blood tests and imaging methods. The blood tests may serve to evaluate the concentration of substances produced by the tumor and the tumor mass can be detected by an ultrasound or computed tomography. Nuclear medicine can also help by administration of a radionuclide that accumulates in tumor cells and marks any tumor metastases.
Small tumors can be successfully treated surgically (removing the tumor tissue). Larger tumors with malignant behavior that have managed to metastasize are treated by a combination of surgery, chemotherapy and biological therapy. Biological therapy, in this case, includes mainly the administration of somatostatin-like substances. Somatostatin is a hormone that can generally block the production of many hormones and active substances including the products of carcinoid cells.