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Signs and Symptoms of Gastrointestinal Carcinoid Tumors

Most gastrointestinal (GI) carcinoids grow slowly. If they do cause symptoms, they tend to be vague. When trying to figure out what’s going on, doctors and patients are likely to explore other, more common possible causes first. This can delay a diagnosis, sometimes even for several years. But some do cause symptoms that lead to their diagnosis.

color illustration of the digestive system which shows the location of the esophagus, stomach, pancreas, transverse colon, descending colon, sigmoid colon, anus, rectum, appendix, cecum, ascending colon, small intestine, gallbladder and liver

Symptoms by tumor location

The symptoms a person can have from a GI carcinoid tumor often depend on where it is growing.

The appendix

People with tumors in their appendix often don’t have symptoms. If the tumor is discovered, it is usually when the appendix is removed for some other problem. Sometimes, the tumor blocks the opening between the appendix and the rest of the intestine and causes appendicitis. This leads to symptoms like fever, nausea, vomiting, and abdominal (belly) pain.

The small intestine or colon

If the tumor starts in the small intestine, it can cause the intestines to kink and be blocked for a while. This can cause cramps, belly pain, weight loss, fatigue, bloating, diarrhea, or nausea and vomiting, which might come and go. These symptoms can sometimes go on for years before the carcinoid tumor is found. A tumor usually has to grow fairly large before it completely blocks (obstructs) the intestine and causes severe belly pain, nausea and vomiting, and a potentially life-threatening situation.

Sometimes a carcinoid tumor can block the opening of the ampulla of Vater, which is where the common bile duct (from the liver) and the pancreatic duct (from the pancreas) empty into the intestine. When this is blocked, bile can back up, leading to yellowing of the skin and eyes (jaundice). Pancreatic juices can also back up, leading to an inflamed pancreas (pancreatitis), which can cause belly pain, nausea, and vomiting.

A carcinoid tumor sometimes can cause intestinal bleeding. This can lead to anemia (too few red blood cells) with fatigue and shortness of breath.

The rectum

Rectal carcinoid tumors are often found during routine exams, even though they can cause pain and bleeding from the rectum and constipation.

The stomach

Carcinoid tumors that develop in the stomach usually grow slowly and often do not cause symptoms. They are sometimes found when the stomach is examined by an endoscopy looking for other things. Some can cause symptoms such as the carcinoid syndrome.

Signs and symptoms from hormones made by carcinoid tumors

Some carcinoid tumors can release hormones into the bloodstream. This can cause different symptoms depending on which hormones are released.

Carcinoid syndrome

About 1 out of 10 carcinoid tumors release enough hormone-like substances into the bloodstream to cause carcinoid syndrome symptoms. These include:

  • Facial flushing (redness and warm feeling)
  • Severe diarrhea
  • Wheezing
  • Fast heartbeat

Many people find that factors such as stress, heavy exercise, and drinking alcohol trigger these symptoms. Over a long time, these hormone-like substances can damage heart valves, causing shortness of breath, weakness, and a heart murmur (an abnormal heart sound).

Not all GI carcinoid tumors cause the carcinoid syndrome. For example, those in the rectum usually do not make the hormone-like substances that cause these symptoms.

Most cases of carcinoid syndrome occur only after the cancer has already spread to other parts of the body. Carcinoid tumors in the midgut (appendix, small intestine, cecum and ascending colon) that spread to the liver are most likely to cause carcinoid syndrome.  

Cushing syndrome

Some carcinoid tumors produce ACTH (adrenocorticotropic hormone), a substance that causes the adrenal glands to make too much cortisol (a steroid). This can cause Cushing syndrome, with symptoms of:

  • Weight gain
  • Muscle weakness
  • High blood sugar (even diabetes)
  • High blood pressure
  • Increased body and facial hair
  • A bulge of fat on the back of the neck
  • Skin changes like stretch marks (called striae)

Zollinger-Ellison syndrome

Carcinoid tumors can make a hormone called gastrin that signals the stomach to make acid. Too much gastrin can cause Zollinger-Ellison syndrome, in which the stomach makes too much acid. High acid levels can lead to irritation of the lining of the stomach and even stomach ulcers, which can cause pain, nausea, and loss of appetite.

Severe ulcers can start bleeding. If the bleeding is mild, it can lead to anemia (too few red blood cells), causing symptoms like feeling tired and being short of breath. If the bleeding is more severe, it can make stools black and tarry. Severe bleeding can be life threatening.

If the stomach acid reaches the small intestine, it can damage the intestinal lining and break down digestive enzymes before they have a chance to digest food. This can cause diarrhea and weight loss.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

National Cancer Institute Physician Data Query (PDQ). Gastrointestinal Carcinoid Tumors Treatment (PDQ®)–Health Professional Version. 2018. Accessed at on August 3, 2018.

Norton JA and Kunz PL. Carcinoid) Tumors and the Carcinoid Syndrome. In: DeVita VT, Hellman S, Rosenberg SA, eds. Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2015:1218-1226.

Pandit S, Bhusal K. Carcinoid Syndrome. [Updated 2017 Oct 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2018 Jan-.  Available from: Accessed August 3, 2018.

Schneider DF, Mazeh H, Lubner SJ, Jaume JC, Chen H. Cancer of the Endocrine System. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff's Clinical Oncology. 5th ed. Philadelphia, Pa: Elsevier; 2014:1112-1142.

Last Revised: September 24, 2018

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