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.

Symptoms by location of the tumor

The symptoms a person develops from a GI carcinoid tumor often depend on where it is.

The appendix

People with tumors in their appendix often don’t have symptoms. If it is discovered, it is usually when they have their appendix removed during an operation 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 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. This can sometimes go on for years before the carcinoid tumor is found. A tumor usually needs to grow fairly large before it completely blocks (obstructs) the intestine. When that happens, patients have severe belly pain, nausea and vomiting.

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.

Sometimes, a carcinoid 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 during an exam of the stomach by an endoscopy looking for other things. (Endoscopy is described later in this section.) 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 create different problems 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 the symptoms of carcinoid syndrome. 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 carcinoids cause the carcinoid syndrome. For example, rectal carcinoids 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. Normally, blood coming from the GI tract first flows through the liver, where substances made by GI carcinoid tumors are broken down before they can reach the rest of the body. This prevents carcinoid symptoms. But if the cancer spreads outside the intestine (such as to the liver or lungs), the substances it makes can enter the main bloodstream and reach other parts of the body, where it can cause symptoms.

Cushing syndrome

Some neuroendocrine tumors produce ACTH (adrenocorticotropic hormone), a substance that causes the adrenal glands to make too much cortisol. 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
  • Hump of fat on back of 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 itself 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 master's-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Medical Review: February 26, 2015 Last Revised: February 8, 2016

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