Introduction:
Several symptoms brought on by neuroendocrine tumors that are well-differentiated and were formerly referred to as carcinoid tumors are together referred to as carcinoid syndrome. Only 10 % of these carcinoid tumors cause carcinoid syndrome. Carcinoid syndrome is most prevalent in carcinoid tumors of the midgut that spread to the liver. Carcinoid tumors of the foregut and hindgut rarely lead to the development of carcinoid syndrome. Medication to prevent over-production of hormones, therapy for the liver, surgical removal of early-stage low-grade tumors, and other treatment options are available for carcinoid syndrome.
What Are Carcinoid Tumors?
Carcinoid tumors are slow-growing neuroendocrine tumors originating in the cells of the neuroendocrine system. These tumors may spread to other parts of the body in some cases. Carcinoid tumors are the most common tumors of the appendix, but they are also associated with the small intestine, rectum, and stomach. Carcinoid tumors have a very slow growth rate compared to other malignant tumors. Carcinoid tumors of the midgut, including jejunum, ileum, appendix, and cecum, are associated with carcinoid syndrome.
What Is Carcinoid Syndrome?
Carcinoid syndrome is a disease consisting of a combination of symptoms, physical changes, and laboratory findings. Carcinoid tumors are the tumors of the midgut, and they are seen in individuals with advanced cases of carcinoid tumors. Carcinoid syndrome occurs in carcinoid tumor cases that have spread to the liver. These tumors are differentiated endocrine tumors with secretory properties; they release serotonin, kallikrein, and other active peptides.
These tumors commonly occur in the intestine and appendix, but about 10 % of them occur in the lungs. Moreover, only 10 % of people with carcinoid tumors will develop carcinoid syndrome. Carcinoid tumors are rare and affect 27 individuals per million, both males and females equally. Carcinoid tumors and carcinoid syndrome can occur at any age, but they most frequently occur in middle age.
What Are the Other Names of Carcinoid Syndrome?
There are several other names for carcinoid syndrome, including:
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Carcinoid apudoma.
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Carcinoid cancer.
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Carcinoid disease.
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Flush syndrome.
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Functioning carcinoid.
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Functioning argentaffinoma.
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Malignant carcinoid syndrome.
What Causes Carcinoid Syndrome?
Carcinoid syndrome occurs in patients with carcinoid tumors, and the exact definitive cause of carcinoid tumors is not known. Carcinoid syndrome occurs when a carcinoid tumor spreads to the liver, lungs, or any other organ. Carcinoid tumors release hormones like serotonin, kallikrein, tachykinins, bradykinin, prostaglandins, etc., and these hormones cause the blood vessels to dilate, and this eventually results in a group of symptoms known as carcinoid syndrome. However, some risk factors like smoking or dietary intake can cause carcinoid tumors.
What Are the Symptoms of Carcinoid Syndrome?
The diagnosis of carcinoid syndrome can be delayed for a long time because, in some cases, the patient remains asymptomatic. However, in patients who do show physical changes, the signs and symptoms of carcinoid syndrome include:
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Flushing: Flushing is the most important clinical finding of carcinoid syndrome; it is episodic warmth and redness of the face. Facial flushing is seen most commonly, along with bright red flushing of the neck and upper chest. Flushing occurs when excess serotonin or other chemicals in the blood cause blood vessels to dilate, this feels warm and uncomfortable.
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Diarrhea: Diarrhea in carcinoid syndrome is often associated with abdominal cramps and discomfort. This symptom is due to the action of serotonin, gastrin, and histamine. Diarrhea is so severe that the body may develop electrolyte imbalance and dehydration.
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Abdominal Pain: Abdominal pain may be due to liver enlargement, bowel obstruction, or lack of oxygen in the small bowel.
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Wheezing: Asthma signs such as wheezing and shortness of breath may occur. This bronchoconstriction is mostly histamine or serotonin-induced. Wheezing is often accompanied by flushing, sneezing, and shortness of breath.
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Carcinoid Heart Disease: Some patients affected by carcinoid syndrome may develop carcinoid heart disease. Carcinoid syndrome may damage the heart valves and eventually cause congestive heart failure.
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Carcinoid Crisis: In rare cases, the acute occurrence of flushing, wheezing, diarrhea, palpitations, weakness, blood pressure changes, etc., constitutes a carcinoid crisis which is a life-threatening condition.
Is Carcinoid Syndrome Fatal?
Carcinoid syndrome can be fatal if the condition progresses to a carcinoid crisis. A carcinoid crisis is a potentially life-threatening condition that can eventually lead to death if immediate medical attention is not provided.
How Is Carcinoid Syndrome Diagnosed?
Diagnosis of carcinoid syndrome is based on a multimodality approach, including biochemical investigations, radiological and nuclear imaging, and tissue biopsy. The diagnosis of carcinoid syndrome is made by the following tests:
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5-HIAA (5-hydroxyindoleacetic): 24 hours of urine excretion of 5-HIAA, which is a product of the breakdown of serotonin, is evaluated.
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Chromogranin-A: This blood test is done in combination with an imaging test known as octreoscan to confirm the diagnosis of carcinoid syndrome.
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CT Scan and MRI: CT scan (computed tomography) and MRI (magnetic image resonance) imaging test may be done on the chest or abdomen.
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Echocardiogram: An echocardiogram (ECG) may be performed to detect any complications of the heart.
How Is Carcinoid Syndrome Treated?
The definitive treatment of carcinoid syndrome is the surgical removal of the carcinoid tumor. Apart from this, symptomatic treatment may be given to the patient:
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Octreotide: It mimics somatostatin and decreases the secretion of serotonin by the tumor.
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Telotristat Ethyl: It is used in combination with Octreotide in patients who do not respond to Octreotide monotherapy. It inhibits and reduces the production of serotonin.
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Peptide Receptor Radionuclide Therapy (PRRT): This therapy targets the peptide receptors to deliver localized treatment.
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Antihistamine Drugs: Drugs like Cyproheptadine may be used.
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Chemotherapy: Endovascular chemotherapy may be given directly to the liver with the help of special catheters mixed with embolic beads.
What Is the Life Expectancy of Carcinoid Syndrome?
The prognosis of carcinoid syndrome may be different from carcinoid tumors without carcinoid syndrome. The outlook also depends on the location of the carcinoid tumor; in cases where the tumor spreads to the liver, the chances of survival decrease. However, the overall prognosis of the condition is highly variable and uncertain, with a 95 % chance of five years survival in localized diseases and about 80 % of five years survival rate in cases where the disease has spread to the liver.
Conclusion:
A carcinoid tumor is a slow-growing, well-differentiated neuroendocrine tumor with secretory properties and a carcinoid syndrome is a group of symptoms caused by carcinoid tumors. When the carcinoid tumor spreads to the liver or any other part of the body, they mostly originate in the midgut. In extreme cases, the carcinoid syndrome may progress to carcinoid crisis which is a life-threatening condition. The diagnosis of carcinoid treatment may be tricky because sometimes the condition remains asymptomatic for a long time. However, timely diagnosis and prompt treatment can help improve the condition.
