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By Mayo Clinic staffCarcinoid tumors are a slow-growing type of cancer that can arise in several places throughout your body. Carcinoid tumors usually appear in the gastrointestinal tract (appendix, stomach, small intestine, colon, rectum) and in the lungs. But, carcinoid tumors can also begin in other organs, including the ovaries and testes.
Carcinoid tumors rarely cause signs and symptoms until late in the disease. Carcinoid tumors can produce and release hormones into your body that cause signs and symptoms such as diarrhea or skin flushing.