Carcinoid Syndrome
(Carcinoid
Tumor)
Medical Author: Dennis Lee, M.D.
Medical Editor: Jay Marks, M.D.
What is a carcinoid tumor?
A carcinoid tumor is a tumor that develops from enterochromaffin cells.
Enterochromaffin cells are hormone-producing cells that normally are found in
the small intestine, appendix, colon, rectum, bronchi, pancreas, ovaries,
testes, bile ducts, liver, as well as other organs. Enterochromaffin cells
produce many types of hormones for example, histamine, serotonin, dopamine, tachykinins,
and other substances that have profound effects on the circulatory system (heart
and blood vessels), the gastrointestinal tract, and the lungs. For example,
serotonin can cause diarrhea, histamine wheezing, and
tachykinins flushing due to dilation of blood vessels.
Since carcinoid tumors develop from enterochromaffin
cells, they frequently retain the capability of producing the same hormones,
often in large quantities. When these hormones circulate in the blood, they can
cause symptoms of carcinoid syndrome, which is discussed later.
The important characteristic of carcinoid tumors that
sets them apart from other gastrointestinal tract tumors is their potential to
cause the carcinoid syndrome. Most other gastrointestinal tract tumors (such as
colon cancers or small bowel lymphomas) cause symptoms primarily due to their
local effects on the intestines such as abdominal pain, intestinal bleeding, and
intestinal obstruction. Although carcinoid tumors may also cause these local symptoms, they
may also produce and release hormones that cause the carcinoid syndrome. Often,
symptoms of the carcinoid syndrome can be more devastating than the local
symptoms.
What is the carcinoid syndrome?
The carcinoid syndrome is a combination of symptoms
caused by the hormones released by the tumors into the blood stream. The
symptoms of the carcinoid syndrome vary depending on which hormones are released
by the tumors. The common hormones released are serotonin, bradykinin (a
molecule produced by enzymes at the site of an injury and then binds to
receptors to cause pain), histamine, and chromogranin A (a general marker for neuroendocrine tumors).
Typical carcinoid symptoms include:
- flushing
- diarrhea
- abdominal pain
- and wheezing due to bronchospasm (airway narrowing)
- valvular heart disease
- surgery can provoke a complication known as carcinoid crisis.
Flushing
Flushing is the most common symptom of carcinoid
syndrome. An estimated 90% of the patients have flushing some time during their
illness. Flushing is characterized by redness or purple discoloration of face
and neck (or upper body) accompanied by a warm sensation. Episodes of flushing
typically occur suddenly, either spontaneously or brought on by emotional
stress, physical stress, or drinking alcohol. Episodes of flushing can last minutes to hours.
Flushing can be accompanied by palpitations, low blood
pressure, or fainting if blood pressure becomes too low to supply blood to the
brain. Rarely, flushing can be accompanied by high blood pressure. Hormones
responsible for flushing have not been clearly identified; possible candidates
include serotonin, bradykinin, and substance P.
Diarrhea
Diarrhea is the second most common symptom of carcinoid
syndrome. An estimated 75% of patients with carcinoid syndrome have diarrhea.
Diarrhea often occurs with flushing but also can occur alone. Diarrhea in the
carcinoid syndrome is most likely caused by the hormone serotonin. Medications
that block the action of serotonin such as ondansetron (Zofran) often alleviates
the diarrhea. Sometimes diarrhea in the carcinoid syndrome can be due to a local
effect of the tumor obstructing the small intestine.
Heart disease
Heart disease occurs in an estimated 50% of patients
with the carcinoid syndrome. Carcinoid syndrome typically causes scarring and
stiffness of the tricuspid and pulmonic valves of the right side of the heart.
Stiffness of these two valves decreases the ability of the heart to pump blood
from the right ventricle to the lungs and to the rest of the body and leads to
heart failure. Typical symptoms of heart failure include an enlarged liver (due
to the backup of blood returning to the failing heart which is unable to pump
all of the blood returning to it), swelling of the feet and ankles (edema), and
swelling of the abdomen due to fluid accumulation (ascites). The damage to the tricuspid and
pulmonic valves of the heart in the
carcinoid syndrome is most likely caused by prolonged exposure to high levels of
serotonin in the blood.
Carcinoid crisis
Carcinoid crisis is a dangerous condition that can occur at the time of
surgery. It is characterized by a sudden and profound drop in blood pressure
causing shock, sometimes accompanied by an abnormally fast heart rate, high
blood glucose, and severe bronchospasm. Carcinoid crisis can be fatal. The best
way to prevent carcinoid crisis is to treat patients undergoing surgery with
somatostatin (see below) before surgery begins.
Wheezing
Wheezing occurs in approximately 10% of the patients with carcinoid syndrome.
It is a result of bronchospasm (constriction of the bronchial airways) caused by
hormones released by the carcinoid tumors.
Abdominal pain
Abdominal pain is common in patients with carcinoid
syndrome. The pain may be due to tumor metastases in the liver, tumor invading
neighboring tissues and organs, or tumor causing bowel obstruction (please see small bowel carcinoid
tumors below).
Next: How common are carcinoid tumors and carcinoid syndrome? »
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