Carcinoid Tumors of the Colon and Rectum

The term "carcinoid tumor" was coined in 1907 by Siegfried Oberndorfer, a scientist who wanted to designate the tumor as cancer-ish. It doesn't qualify as a benign tumor since it has the ability to metastasize, but it also grows very slowly and seldom spreads, which makes it more benign than most cancers.

A carcinoma is a cancerous tumor and the suffix "-oid" is used to indicate that something resembles something else. So, the term Oberndorfer came up with, "carcinoid tumor," described a tumor that was "cancerous tumor-like." In reality, carcinoid tumors are cancers, but the name "carcinoid" has stuck to this day.

Caucasian doctor and patient using digital tablet at home
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Carcinoid tumors develop from a certain type of neuroendocrine cell, which makes hormones that help regulate digestion. Although carcinoid tumors are the most common type of neuroendocrine tumor, they account for less than one percent of all colorectal cancers. Most carcinoid tumors of the GI tract occur in the small intestine, rectum, and appendix. When they do occur in the colorectal tract, they are about twice as likely to occur in the rectum than in the colon.

Carcinoid tumors grow slowly and have only about a 1 in 300,000 chance of metastasizing (spreading to other locations in the body).


The symptoms, if any, that carcinoid tumor may cause will depend on their location in the colorectal tract. If in the colon, a person may experience abdominal pain and weight loss with no known reason. If in the rectum, a carcinoid tumor may cause blood in the stool, pain in the rectum, and/or constipation.

In patients without spread to the liver, the serotonin and other hormones released by the GI carcinoid tumor will be broken down in the intestinum to inactive substances and effectively destroyed. However, if the tumor has spread to the liver, ovaries, or retroperitoneum, and liver enzymes can no longer destroy the excess hormones, they accumulate in the body and cause the debilitating symptoms of carcinoid syndrome. This condition is characterized by a unique cluster of symptoms, including:

  • Redness in the face and neck
  • A feeling of warmth in the face and neck
  • Abdominal pain
  • Feeling bloated
  • Diarrhea
  • Wheezing
  • Rapid heartbeat

Diagnosis and Treatment

The earlier they are caught, the better the outcome usually will be for patients who have carcinoid tumors. In fact, if they are caught before they spread, carcinoid tumors can often be surgically removed in their entirety and a patient can be considered cured. However, because carcinoid tumors develop so slowly and cause few and vague symptoms, catching them early is a challenge. Once the tumor has spread to other areas of the body, surgery, as well as other treatments, may be needed, either alone or in combination. Other treatments may include medications, chemotherapy, radiation, and ablation.

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  • A Review of Carcinoid Cancer. Carcinoid Cancer Foundation. Jan 2005.
  • ​Sources:
  • Spread, C. and Berkel, H. "Colon Carcinoid Tumors. A Population-Based Study." Diseases of the Colon and Rectum 37.5 (May 1994): 482-491. PubMed.