What Are Carcinoid Tumors of the Lung?

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Carcinoid lung tumors, also known as lung carcinoids, account for about 1% to 2% of lung cancers. These tumors, their risk factors, and their symptoms are different from non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), which are the more common types of lung cancer. For example, younger people and non-smokers are more likely to develop carcinoid lung tumors.

If you've been diagnosed with carcinoid lung tumors, it's important that you understand the unique aspects of this type of cancer, keeping in mind that your experience will be different than that of most other lung cancer patients. It will not be an easy journey, but the survival rate with a lung carcinoid cancer is better than that of other types of lung cancer.

Types of Carcinoid Tumors of the Lung

Carcinoid tumors are a form of neuroendocrine tumor. Neuroendocrine cells are found throughout the body, including the lungs. If these cells multiply excessively, they form small carcinoid tumors. These tumors can form in organs throughout the body. Only 3 out of 10 carcinoid tumors are found in the lungs.

Carcinoid tumors of the lung are divided into two primary types: typical and atypical.

types of carcinoid lung tumors
Verywell / Emily Roberts
  • Typical carcinoid tumors: Typical carcinoids or low-grade carcinoids are made up of cells that appear very much like normal cells. Accounting for roughly 90% of lung carcinoids, these tumors tend to grow slowly and rarely spread beyond the lungs.
  • Atypical carcinoid tumors: Atypical or intermediate grade carcinoids have cells that are more abnormal-appearing. These tumors tend to grow and spread a little faster than typical carcinoids but are usually less aggressive than the more common types of lung cancer.

Lung Carcinoid Tumor Symptoms

Carcinoid tumors of the lung, especially typical carcinoids, tend to grow centrally near the large airways. Because of the location, about 66% of people notice symptoms early in the disease course. For the other 34%, the tumors may grow so slowly that symptoms might not be noticeable for years. In these instances, the cancer may only be found early if you have a test (like a chest X-Ray) for another reason.

When symptoms are present, they're usually related to airway obstruction and might include:

Recurrent lung infections such as bronchitis and pneumonia may also occur if a large tumor blocks the airway. Your healthcare providers may become concerned that you could have cancer if your infection persists despite antibiotic treatment.

Less commonly, carcinoids may present with symptoms of advanced cancer such as loss of appetite and weight loss.

Related to Hormone Secretions

Some carcinoid tumors secrete hormones or hormone-like substances into the bloodstream.

Syndromes that can be brought on by these hormone secretions include carcinoid syndrome and Cushing's syndrome, which can give rise to a number of symptoms that are not usually associated with lung cancer.

  • Carcinoid syndrome: Some carcinoids release substances such as serotonin that cause facial flushing (which can be very prominent), wheezing, and watery diarrhea.
  • Cushing's syndrome: The hormone adrenocorticotropic hormone (ACTH) may be secreted, which causes the symptoms of Cushing's syndrome such as weight gain, a moon-like appearance of the face, accumulation of fat between the shoulders ("buffalo hump"), high blood pressure, and muscle weakness.

In addition, rare effects can also occur as a result of hormonal secretions from carcinoid tumors. These include:

  • Hypercalcemia: Tumors may secrete substances that cause an increased calcium level in the blood. This can lead to weakness, cramping, nausea, and lethargy. When severe, you may lose consciousness.
  • Acromegaly: Carcinoids that secrete growth hormone may result in enlargement of the hands and feet as well as facial changes (acromegaly in adults) or rapid growth (in children).

Overall, carcinoids are a very heterogeneous group of cancers, which means the cells within a tumor and from one tumor to another differ significantly. This can lead to multiple systemic effects and the need for more than one treatment strategy.

Causes and Risk Factors

The causes and risk factors of carcinoid lung tumors are not known. Unlike other pulmonary diseases, smoking and air pollutants don't seem to be associated with it.

Some factors that have been observed include:

  • Sex: It's more common in women than in men.
  • Race: White people are more likely than any others to develop the tumors.
  • Genetics: People with a rare inherited disorder called multiple endocrine neoplasia type 1 (MEN1) seem to have a higher risk for lung carcinoids.
  • Age: Typical and atypical carcinoids can occur at any age, but they are usually found between the ages of 45 and 55, which is slightly younger than the average age of diagnosis for other lung cancers. It is also the most common type of lung cancer found in children.

Diagnosis

The diagnosis of carcinoid tumors is sometimes challenging early on. For example, carcinoid tumors that secrete ACTH may have symptoms that are almost identical to Cushing's syndrome before any lung symptoms occur.

Imaging

If your healthcare providers is concerned that you could have lung cancer or another pulmonary related disorder, you might need to have diagnostic tests.

These tests may include:

  • Chest X-ray: Carcinoid tumors may appear on X-rays, but will be missed if they are small or hidden.
  • Chest computed tomography (CT) scan: A chest CT is more effective for detection of carcinoid tumors, determining their precise size, and pinpointing their location.
  • Somatostatin receptor scintigraphy: This test uses a radioactive particle attached to octreotide, which is injected into the body. Octreotide binds to carcinoid tumors, and gamma rays from the radioactive particle are then visualized to find the tumor. In addition to showing the location of tumors, this test can help in determining the best treatment options.
  • Ga-68 Dotate PET scans: With this type of positron emission tomography (PET) scan, a small amount of a radioactive drug called Dotatate is given by injection before the scan. Dotatate attaches to neuroendocrine tumors (NETs) and shows up on the PET image as bright spots. This test has been shown to be very effective at finding carcinoid tumors.

A CT scan (magnetic resonance imaging, MRI) may also be done to check whether the malignancy has metastasized (spread) to the liver, which is a common site for metastasis of carcinoid lung tumors.

Biopsy

Your healthcare providers will need a tissue sample to confirm your diagnosis and determine the stage of your carcinoid lung tumor.

There are two main types of biopsies for evaluating carcinoid lung cancer:

  • Bronchoscopy: During a bronchoscopy, a flexible tube is inserted through the mouth and threaded down into the large airways (bronchi) of the lungs. Since many carcinoids are located near the airways, these tumors can often be seen via the camera and a biopsy can be taken.
  • Lung biopsy: Your healthcare providers may obtain a biopsy sample using a needle biopsy with a fine needle that's inserted through the chest wall. Or you may have an open lung surgical biopsy, in which a small piece of your tumor is sampled directly during a surgical procedure.

Blood Tests

Blood tests may detect hormones secreted from some carcinoid tumors.

Another test, the Ki67 proliferation index, can sometimes help distinguish carcinoids from other types of lung cancer, as well as predict which carcinoid tumors may respond to chemotherapy (most do not).

Staging

Unlike more common lung cancers, staging tests are not always needed with carcinoid tumors since they grow slowly and are unlikely to spread. Since most carcinoid tumors are slow-growing and have low metabolic activity, they are unlikely to show up as malignant on a PET scan.

Treatment

Since carcinoid tumors can differ from each other, the treatment options vary. At the early stage of the disease, surgery is usually considered the best treatment. Several medications are currently approved for treatment of advanced carcinoid tumors.

Surgery

The type of lung cancer surgery you may need depends on how large the tumors are and where they are located in your lung.

For small tumors, a lobectomy or even a wedge resection may be considered. For larger tumors (or those in certain locations), removal of an entire lung (pneumonectomy) may be recommended.

Biological Therapy

The biological therapy drug Afinitor (everolimus) is recommended for advanced typical and atypical carcinoids that do not secrete hormones or hormone-like substances.

This targeted drug works by interrupting the body's signaling pathway that promotes cancer growth. It's taken as a daily pill, and it may improve survival.

Somatostatin Analogues

The drugs Sandostatin (octreotide), Somatuline (lanreotide), and Signifor (pasireotide) are somatostatin analogs and are used for treating low-grade carcinoid tumors that secrete hormone-like substances. They can control tumor growth and reduce symptoms but are not curative.

You might want to consider enrolling in a clinical trial so you can have access to emerging treatments for your carcinoid tumor.

Prognosis

When carcinoid tumors can be removed surgically, the prognosis is relatively good. With advanced disease, the approval of Afinitor has increased survival, and other treatments are being examined as well.

The five-year survival rate for loco-regional stages of lung carcinoid tumor is approximately  90%. If the cancer is diagnosed in the earliest stages, the survival five-year rate increases to 97%.

Carcinoid tumors associated with the genetic syndrome MEN1 tend to be more aggressive and have lower survival rates.

Coping and Support

Since carcinoid tumors are relatively uncommon, it's important that you find a healthcare provider who is familiar with the disease.

Some of the larger cancer centers, such as the National Cancer Institute-designated centers, are often more likely to have oncologists on staff who have treated a number of other people with these cancers. These larger centers are also more likely to offer you the opportunity to be part of a clinical trial or to receive a newer treatment for advanced carcinoids.

The Carcinoid Cancer Foundation is a non-profit organization committed to supporting people with carcinoid tumors. It can be a resource to help you find a support group or contacts who can answer questions and encourage you as you look for answers and begin treatment.

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10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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