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 are different from the more common types of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). With a carcinoid tumor, lung cancer symptoms may differ significantly from typical types of NSCLC and SCLC. Risk factors also vary, with younger people and non-smokers being more likely to develop this type of lung cancer.

If you've been diagnosed with carcinoid lung tumors, you should research the unique aspects of the cancer, keeping in mind that your experience will be different than most other lung cancer patients. It will not be an easy journey, but the survival rate for lung carcinoids should be much better than for other types of the disease.

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 grow too quickly, 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. This results in about 66% of people noticing symptoms early in the disease's manifestation. For the other 34%, the tumors may grow so slowly that no symptoms will be noticed for years. In these instances, the cancer may only be found early if your doctor is doing a test for another reason.

When symptoms are present, they're usually related to the obstruction of the airway. The symptoms might include:

Recurrent lung infections such as bronchitis and pneumonia may also occur if a large tumor blocks the airway. Doctors may only begin to suspect cancer after antibiotic treatments, meant to help with an infection, fail to solve the problem.

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 that are released into the bloodstream.

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

  • 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 disorders 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 disorders and the need for more than one treatment strategy.

Causes and Risk Factors

It's unclear to researchers what factors cause carcinoid lung tumors or increase your risk of developing this type of cancer. 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 in people 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 the gradual appearance of symptoms that are almost identical to Cushing's syndrome before any lung symptoms occur.

Imaging

If doctors suspect lung cancer or another pulmonary related disorder, they may order imaging tests to check for tumors. These tests may include:

  • Chest X-ray: Carcinoid tumors may appear on X-rays, but will be missed if they are too small or hidden.
  • Chest computed tomography (CT) scan: A chest CT is better able to detect carcinoid tumors and provide details about the precise size and 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 detected to find the tumor. In addition to showing the location of tumors, this test can help identify 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 spread to the liver, which is a common site for carcinoid lung tumors to metastasize (spread) to.

Biopsy

Doctors will need a tissue sample to confirm the diagnosis and determine the stage of your carcinoid lung tumor. There are two main types of biopsies performed:

  • Bronchoscopy: In 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: Doctors may perform a needle or surgical biopsy to get a tissue sample. A needle biopsy may be done by inserting a fine needle through the chest wall and taking a sample of the tumor. In an open lung biopsy, a tumor is biopsied directly during surgery.

Blood Tests

Tests for the hormones that are sometimes secreted may be done for some carcinoid tumors.

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

Staging

Unlike the 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 (have low metabolic activity) they are unlikely to show up as malignant on a PET scan.

Treatment

Since carcinoid tumors can vary significantly, the treatment options can also vary. At the early stage of the disease, surgery is the first choice. For advanced carcinoid tumors, there are several drugs currently approved.

Surgery

The first course of treatment is surgery, but the types of lung cancer surgery recommended will depend on how large the tumors are and where they are located in the 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.

The targeted drug works by interrupting a signaling pathway that is needed for cancer to grow. It may improve survival. It's taken as a daily pill rather than as an intravenous therapy.

Somatostatin Analogues

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

There are a number of options for clinical trials evaluating promising new treatments for carcinoids. Examples include radioactive particles combined with octreotide.

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 studied actively.

The five-year survival rate for a specific stage of lung carcinoid tumor is 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 with lower survival rates.

Coping and Support

Since carcinoid tumors are relatively uncommon, it's important to find a physician 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 clinical trials looking at the newer treatments for advanced carcinoids.

The Carcinoid Cancer Foundation is a non-profit organization committed to supporting people with carcinoid tumors alone. By reaching out to them, you may be able to find a support group or contacts who can help answer questions and encourage you as you look for answers and begin treatment.

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