A lung carcinoid tumor is a rare type of lung cancer not usually associated with smoking. Carcinoids are tumors that develop from neuroendocrine cells found in different parts of the body, such as the lungs and digestive tract.

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While some people may not experience symptoms of carcinoid lung tumors, others may experience breathing symptoms such as shortness of breath and coughing.

Hormone-like symptoms are also possible and may include excessive male-pattern hair growth in females and facial flushing.

The only treatment for carcinoid lung tumors is surgery. Some doctors may also recommend chemotherapy and radiation.

This article will look at the symptoms, stages, and treatment of lung carcinoid tumors.

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Carcinoid lung tumors are a type of lung cancer that doctors sometimes call lung carcinoids. They are a rare, slow-growing type of lung cancer.

People start developing carcinoid lung tumors in a certain type of body cell called a neuroendocrine cell.

Neuroendocrine cells found in the lungs are like nerve cells found in the brain and spinal cord. They also act like hormone-making cells.

Neuroendocrine cells are not part of a single organ but are spread across different parts of the body. Within the lungs, neuroendocrine cells:

  • help control air and blood flow
  • help control the growth of other lung cells
  • detect oxygen and carbon dioxide levels in inhaled air and release chemicals to help the lungs adjust

While there are different types of lung cancers, only cancers that develop from neuroendocrine cells in the lungs are called lung carcinoids.

Doctors have identified two types of lung carcinoid tumors: typical and atypical carcinoids.

About 25% of people with carcinoid lung tumors may not experience any symptoms. Doctors may find the cancer when testing a person for another medical condition. Symptoms of carcinoid lung tumors may include:

  • coughing or wheezing
  • blood in phlegm
  • symptoms of pneumonia
  • facial flushing
  • shortness of breath
  • high blood pressure
  • weight gain
  • asthma-like symptoms
  • excessive growth in females of dark or coarse hair in a male pattern

According to the American Cancer Society, typical carcinoid tumors are the most common among the different types of lung carcinoid tumors. Smoking does not seem to cause typical carcinoids in the lung.

Typical carcinoids grow slowly and do not usually spread outside of the lungs.

Atypical carcinoids are different from typical carcinoids because they grow faster and may spread to other body organs. They develop more commonly in people who smoke compared with typical carcinoid lung tumors.

Healthcare professionals class typical carcinoids as low-grade tumors or stage 1a tumors, and atypical carcinoids as intermediate-grade tumors.

According to the American Cancer Society, researchers are unsure what causes carcinoid lung tumors.

Many of the factors that lead to more common lung cancer, called carcinomas, do not seem to cause carcinoid tumors.

Doctors may find early signs of carcinoid lung tumors when doing lung biopsies for other medical conditions.

“Tumorlets” in the lungs are small clusters of neuroendocrine cells that resemble lung carcinoid tumors. Most often, tumorlets do not develop into carcinoid tumors, but sometimes they do.

Researchers have identified certain alterations in chromosomes and genes of cells in carcinoid lung tumors that may affect how the cells function. Today, it is not yet clear how these changes lead to tumor development.

Doctors are also unsure whether certain risk factors exist for lung carcinoid development. Some people who develop lung carcinoid tumors may not have any risk factors to explain their condition.

Risk factors for carcinoid lung tumors include:

  • being female
  • being white
  • being aged between 45–55 years old
  • having multiple endocrine neoplasia type 1, an inherited disease that puts people at risk for tumors in endocrine organs
  • having a family history of lung carcinoid tumors
  • tobacco smoke (for atypical carcinoids)

Many of these risk factors are things that people cannot change.

Since doctors are unsure of the causes and risk factors of carcinoid tumors, it is unknown how to prevent this type of cancer.

Since about one-quarter of people with carcinoid lung tumors do not have any symptoms, doctors must use other diagnostic tools to diagnose carcinoid lung tumors.

Doctors will check for hormone abnormalities if they suspect a neuroendocrine tumor. These include:

  • urinary dU-5-hydroxy indol-acetic acid
  • 24-hour urine free cortisol
  • blood cortisol
  • adrenocorticotropic hormone in people with Cushing’s disease
  • growth hormone-releasing hormone and insulin growth factor in people with acromegaly

Bronchoscopy and biopsy are the gold standard for diagnosing carcinoid lung tumors.

Bronchoscopy allows doctors to see the inside of the lungs to check for abnormal growths. If a doctor finds a growth, they can remove a piece of it for analysis.

Doctors can also use medical imaging to detect carcinoid lung tumors. According to a 2021 article, radiologists may find carcinoid lung tumors on a chest X-ray in about 40% of cases.

The gold standard for detecting lung carcinoids with medical imaging is a CT scan.

Fluorodeoxyglucose PET scans help to distinguish typical from atypical carcinoid lung tumors.

Some doctors may order octreotide single-photon emission CT scans and other new imaging techniques, which can be more sensitive at detecting carcinoid lung tumors.

When diagnosing carcinoid lung tumors, doctors must distinguish between typical and atypical tumors. This distinction is necessary for selecting the correct treatment.

People with lung carcinoids will require surgery to remove the abnormal growth. Some may require extensive removal if they have atypical carcinoids. Surgeons will remove an entire lobe of the lung.

In other situations, people may require bronchoplasty, which involves repairing the bronchi of the lungs.

Some people may require additional therapy for advanced atypical lung carcinoids. This may include chemotherapy with or without radiation therapy.

Certain cancer societies also recommend additional therapy for atypical carcinoids with abnormal lymph nodes.

According to a 2021 article, the most important factor that affects the outlook of carcinoid lung tumors is whether the cancer is typical or atypical. Another factor affecting outlook is older age and lymph node involvement in people with atypical lung carcinoids.

Atypical lung carcinoids are more likely to spread to other parts of the body than typical lung carcinoids. The 2021 article suggests that spreading to other parts of the body occurs in 20% of atypical cases.

According to a 2018 article, the 5-year overall survival rate for typical carcinoids post-surgery is between 87–100%. The 5-year overall survival rate for atypical carcinoids is between 40–90%.

Lung carcinoid tumors develop from abnormal neuroendocrine cells in the lungs. They may be typical or atypical.

Typical lung carcinoids are more common, and usually do not spread outside of the lungs. Atypical tumors may grow more quickly and spread to other parts of the body.

Doctors will diagnose carcinoid lung tumors with biopsies, blood and urine samples, and medical imaging. Once diagnosed, people require surgery to remove the growth. Some doctors may recommend additional treatment.