Carcinoid Tumors

Home » Carcinoid Tumors » Overview, Incidence and Prevalence, Causes and Risk Factors, Signs and Symptoms

Overview

Carcinoid tumors, or carcinoids, originate in hormone-producing cells of the gastrointestinal (GI) tract (i.e., esophagus, stomach, small intestine, colon), the respiratory tract (i.e., lungs, trachea, bronchi), the hepatobiliary system (i.e., pancreas, gallbladder, liver), and the reproductive glands (i.e., testes, ovaries).

The most common site of origin is the GI tract and carcinoid tumors often develop in the appendix, the rectum, and the lower sections of the small intestine (i.e., the jejunum and the ileum). The large tubes that lead from the windpipe to the lungs (bronchi) are other common sites of origin.

Carcinoids are classified as neuroendocrine tumors. They develop in peptide- and amine-producing cells, which release hormones in response to signals from the nervous system. Excessive amounts of these hormones cause a condition called carcinoid syndrome in approximately 10% of patients with carcinoid tumors.

Carcinoids are slow growing and tumors with the same site of origin often have different characteristics and growth patterns. They can be subdivided according to the following:

• Cellular growth pattern (e.g., trabecular, glandular, undifferentiated, mixed)
• Hormones produced (e.g., bradykinin, serotonin, histamine, prostaglandins)
• Site of origin – foregut (respiratory tract, pancreas, stomach, first section of the small intestine [duodenum]), midgut (jejunum, ileum, appendix, diverticulum, ascending colon), or hindgut (transverse colon, descending colon, rectum)

Incidence and Prevalence
According to the American Cancer Society, approximately 5,000 carcinoid tumors are diagnosed each year in the United States. According to the National Cancer Institute (NCI), approximately 74% of these tumors originate in the GI tract and 25% occur in the respiratory tract.

Carcinoids are rare in children and are more common in patients older than the age of 50. They are twice as common in men. Carcinoid tumors of the appendix usually are benign and often occur between the ages of 20 and 40.

Causes and Risk Factors

The cause of carcinoid tumors is unknown, but a genetic link is suspected. Multiple endocrine neoplasia type 1 (MEN1) is a genetic disorder that increases the risk for neuroendocrine tumors, including carcinoids. Gastrointestinal conditions (e.g., peptic ulcer disease, pernicious anemia, atrophic gastritis, Zollinger-Ellison syndrome) increase the risk for carcinoid tumors of the GI tract.

Unlike other types of lung cancer, carcinoids of the respiratory tract are not related to smoking.

Signs and Symptoms

Symptoms of carcinoid tumors depend on the site of origin, on whether or not the tumor has spread (metastasized), and on which hormones are produced by the tumor.

Carcinoid tumors that are confined to the GI tract may not cause symptoms (i.e., be asymptomatic) because the hormones produced by these tumors are released into the bloodstream and destroyed by the liver. In some cases, these tumors result in symptoms caused by obstruction, such as abdominal pain, weight loss, changes in bowel function (e.g., constipation, diarrhea), and GI bleeding.

Tumors that originate in or spread (metastasize) to areas other than the GI tract (e.g., liver, lungs, pancreas) produce hormones that are not destroyed in the liver. When excessive amounts of these hormones circulate through the body, carcinoid syndrome can result

Carcinoid patients have an increased risk for Cushing's syndrome, a disease caused by excess production of hormones by the adrenal glands; somatostatinoma syndrome, a condition caused by excess production of somatostatin; and additional cancerous (malignant) tumors.

Common sites of carcinoid metastases include lymph nodes, liver, lungs, and bone. The likelihood of metastasis varies according to the size of the tumor. In carcinoid tumors less than 1 cm, the rate of metastasis is about 15–25%; in tumors between 1 and 2 cm, the rate is about 58–80%; and in tumors larger than 2 cm, the rate is more than 70%.

Carcinoid Syndrome

When carcinoid tumors produce excessive amounts of hormones that circulate throughout the body, a condition called carcinoid syndrome can occur. This syndrome, which develops in approximately 10% of patients, is more common in carcinoids of the midgut, the foregut, and in those that have metastasized (especially to the liver). Symptoms of carcinoid syndrome depend on which hormones are produced by the tumor.

During the course of the disease, approximately 70% of carcinoid syndrome patients experience a sudden red rash that usually develops on the face and neck and is accompanied by feelings of warmth and itching (called flushing). Episodes of flushing may be spontaneous or may be triggered by stress, alcohol, exercise, or consumption of certain foods, such as cheese.

Other symptoms of carcinoid syndrome include the following:

• Abdominal pain
• Bluish tint to the skin (cyanosis)
• Diarrhea
• Enlargement of peripheral body parts including face, head, hands, and feet (acromegaly)
• Erectile dysfunction
• Fever
• Heart damage (e.g., endocardial fibrosis)
• Malnutrition (caused by malabsorption of foods)
• Reduced sex drive (libido)
• Skin lesions
• Wheezing

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