Most carcinoids grow slowly. The 5-year survival rate following surgical removal (resection) of a carcinoid tumor that has not metastasized is 70—90%. In approximately 45% of patients, metastases are present at the time of diagnosis. Patients with metastatic disease often live 10—15 years. Because carcinoid tumors usually grow and spread slowly, about half of all gastrointestinal carcinoid tumors are found at an early or localized stage, usually before they cause any problems.

In many cases, carcinoid tumors are found incidentally when looking for something else. The tumors don’t cause any symptoms but are found during tests done for other diseases or because parts of the digestive system are removed to treat other diseases.

For example, a person with stomach symptoms may have a test called an upper endoscopy, where the doctor looks at the stomach lining through a flexible lighted tube. During this test, the doctor may incidentally notice a small bump in the stomach wall that turns out to be a carcinoid tumor.

Sometimes during colorectal cancer screening a routine sigmoidoscopy or colonoscopy (looking at the large bowel through a flexible lighted tube) will incidentally find a small carcinoid tumor.

When a person’s appendix is removed to treat appendicitis (inflammation of the appendix), doctors may incidentally find a small carcinoid, as well as the expected inflammation. Some studies have found that about 1 of every 300 people who have appendix surgery done for other diseases turn out to have a tiny carcinoid near the tip of their appendix. In most of these cases, the carcinoid was too small to have caused any symptoms.