Most carcinoid tumors start in the gut, including the intestines, appendix, rectum, colon, stomach, and pancreas. They account for about one-third of all tumors of the small intestine and almost 50% of all malignant tumors of the small intestine. Yet these tumors can also be found in the lungs, ovary, and elsewhere.
Carcinoid tumors are a type of neuroendocrine tumor, which means they come from cells of the nervous and endocrine system, and can produce hormones. When they secrete excess hormones such as histamine and serotonin, they can cause symptoms such as flushing, stomach cramps, and diarrhea. This is called carcinoid syndrome.
Like most other types of cancer, carcinoid tumors are most easily treated when found early. In fact, in the early stages they can often be completely cured through surgery. Most carcinoid tumors grow and spread very slowly. But because these tumors often don't cause any symptoms for many years, early detection can be tricky.
Signs and Symptoms of a Carcinoid Tumor
When carcinoid tumors do cause symptoms, they may be vague, or may be similar to symptoms of other medical conditions.
Carcinoid tumors can also lead to two conditions: Carcinoid syndrome and Cushing's syndrome.
"The biggest obstacle in diagnosing carcinoid tumors is not thinking of them," says Richard Warner, MD, professor of medicine at the Mount Sinai School of Medicine and medical director of the Carcinoid Cancer Foundation. "Because carcinoid tumors are not so common, doctors may not think of them as a possibility when they see these symptoms."