What is Lung Carcinoid Tumors?
Carcinoid tumors are uncommon cancers that start in cells that produce hormones, and they can be found in different places throughout your body– like in your digestive system, lungs, ovaries, adrenal glands, and thyroid. However, they mostly appear in the lungs, making up about a quarter of all carcinoid tumor cases. Still, these form less than 2% of all types of lung cancers.
There are two main kinds of lung carcinoid tumors: “typical” and “atypical”. The atypical kind only makes up 10-15% of these cases. Typical carcinoids are slow-growing while atypical ones grow at a medium pace. These types are defined based on their appearance under a microscope and other factors by the World Health Organization.
Mostly, these carcinoid tumors (about 80%) are found in the middle of the lung, while the remaining 20% are found around the edges. All lung carcinoid tumors can be cancerous and have the ability to spread to other regions. Unlike many lung cancers, these are not linked with smoking habit. These tumors are usually small and occur in the central locations of the body. In fewer than 10% of cases, the lymph nodes – small glands that filter the body’s fluid called lymph – are also involved. It’s also rare for these tumors to cause a group of symptoms, collectively referred to as carcinoid syndrome, which results from chemicals the tumor releases; this happens in less than 3% of cases.
What Causes Lung Carcinoid Tumors?
The exact reasons why carcinoid tumors develop aren’t entirely clear. Some research suggests that smoking might have some connection, but it’s not really certain yet. Interestingly, studies have found a higher number of smokers among those with atypical (or unusual) carcinoid tumors compared to the typical ones. It’s also been observed that certain air pollutants or chemicals might increase the risk of these tumors.
In some rare instances, lung carcinoid tumors can appear along with a condition known as multiple endocrine neoplasia type 1 (MEN-1). This is a syndrome where tumors occur in endocrine glands (the glands in the body that produce hormones). There have also been sporadic instances where the MEN-1 gene is found to be ‘turned off’ or inactivated in people with carcinoid tumors, which hints at a possible genetic influence on the development of these tumors.
Risk Factors and Frequency for Lung Carcinoid Tumors
Carcinoid tumors are rare forms of cancer that can affect the lungs. Though they can appear at any age from 5 to 90, they are typically found around the age of 50. Some types of these tumors may be diagnosed 10 years earlier. Interestingly, they are the most common type of lung tumor found in children, representing about 8% of cases in their second decade of life.
Studies show that these tumors are more frequently found in people of white ethnicity and in women as compared to men. In recent years, there has been an increase in the number of carcinoid tumor cases, including those affecting the lungs. This rise is likely due to improvements in medical technology and better ability to detect these tumors.
- Carcinoid tumors are rare, but can affect the lungs.
- They can occur at any age from 5 to 90, but typically are diagnosed around age 50.
- Some forms of these tumors can be found 10 years earlier.
- They are the most common lung tumor in children, making up about 8% of cases in their second decade of life.
- These tumors are found more often in those of white ethnicity and in women.
- The increase in these tumor cases in recent years is likely due to advances in medical technology and improved detection rates.
Signs and Symptoms of Lung Carcinoid Tumors
About a quarter of people with lung carcinoid tumors don’t have any noticeable symptoms. These tumors are frequently found by chance during tests for other health problems.
The most usual symptoms of bronchopulmonary carcinoid tumors include:
- Coughing or wheezing
- Coughing up blood
- Symptoms due to the tumor blocking the airway, which may lead to lung collapse or pneumonia
As these are primarily carcinoid tumors, they can cause what’s known as carcinoid syndrome. The symptoms of this can include:
- Redness in the face (flushing)
- Difficulty breathing
- High blood pressure
- Weight gain
- Excessive hair growth
- Symptoms like those of asthma
Small carcinoids often don’t cause symptoms and are often discovered by chance during medical check-ups or imaging tests for other reasons.
Pulmonary carcinoid tumors usually don’t cause symptoms related to hormone production, meaning these tumors are often “endocrinologically silent”. In other words, they don’t often make significant levels of hormones or bioactive substances that cause noticeable effects. Clinically noticeable syndromes because of peptide production are rare, but they can include carcinoid syndrome, Cushing syndrome, and acromegaly.
Testing for Lung Carcinoid Tumors
If your doctor suspects that you might have a carcinoid tumor, they will start to run some tests. The tests can include measuring certain chemicals in your blood like chromogranin A, as well as checking your blood count, electrolytes, and the functioning of your liver and kidneys. All these are designed to help doctors figure out what could be going on in your body.
If you’re showing symptoms that suggest the tumor might be releasing hormones, the doctor could order additional tests. For instance, they might check your urine for a chemical called 5-hydroxy indoleacetic acid (5-HIAA), which is often high in people with carcinoid syndrome. To look for signs of Cushing’s disease, they might perform tests to check the levels of cortisol and a hormone called adrenocorticotropic hormone (ACTH) in your body. They can also measure the levels of growth hormone-releasing hormone (GHRH) and insulin growth factor (IGF)-I if they suspect you might have acromegaly, a condition where your body produces too much growth hormone.
For lung carcinoids in particular, a procedure called a bronchoscopy is often used. This involves the doctor inserting a thin tube with a camera into your lungs to look for any tumors. However, this procedure does carry a slight risk of bleeding because these tumors have plenty of blood vessels.
If the doctor wants to get a clearer image of what’s going on, they might take x-rays of your chest or do a computed tomography (CT) scan, which uses x-rays to create detailed images of the inside of your body. These scans can often show the tumors as well-defined, round masses, and sometimes, there may be signs of calcification (hardening) in the central part of the tumor. If the tumor affects your bronchial airway, the scans might show things like atelectasis (a condition where the air sacs in the lungs collapse), bronchiectasis (a condition where the airways in your lungs get wider and inflamed), or areas of hyperlucency, which means the tissues appear unusually bright on CT scans.
Another scanning technique called Fluorodeoxyglucose (FDG) positron emission tomography (PET) may be used to clearly tell the difference between carcinoid tumors and other types of neuroendocrine tumors, which are a group of conditions where certain cells become cancerous. On a PET scan, carcinoids typically show low-to-moderate activity.
A scan called Octreotide single-photon emission CT (SPECT), and newer imaging techniques using gallium-labeled somatostatin analogs, may be better at detecting lung carcinoids. Somatostatin receptors imaging using Indium-111-labeled-octreotide also increases sensitivity for diagnosis, staging, and follow-up for recurrence.
Treatment Options for Lung Carcinoid Tumors
Surgery is usually the top choice of treatment for lung carcinoids, which are rare neuroendocrine tumors that start in the lungs. How much surgery depends on a few factors. This includes whether the carcinoid is typical or atypical – with atypical being rarer and more aggressive – and how much the surrounding lung tissue is affected.
In cases where the carcinoid is atypical or the lower part of the lung is heavily affected, extensive surgery might be necessary. The surgical technique that is often the first choice is called a lobectomy, which is the removal of an entire lobe of the lung. However, in some cases, other techniques like sleeve resection or wedge resection could also be performed.
Carcinoids often begin in the main or lobe bronchi, which are the large air passages that lead from the windpipe into the lungs. Due to this, bronchoplastic procedures are usually needed during surgical resection. This is done to safeguard the lung’s function and ensure the continuity of airways.
A preferred surgical approach for carcinoids located on the periphery of the lungs is the ‘wedge resection’. This procedure involves removing a small, wedge-shaped portion of the lung, and is typically enough for these kinds of cases.
There is ongoing debate about the use of adjuvant therapy – additional treatment given after surgery to lower the risk of the carcinoid coming back – in managing pulmonary carcinoids. No agreement has been reached on this subject yet. However, recommended guidelines imply that those patients with atypical carcinoids in stage III might benefit from adjuvant chemotherapy, with or without radiation. Adjuvant treatment is also advised for atypical carcinoids, if lymph nodes are positive but not for the typical variant.
Systemic therapy, which refers to treatment involving the entire body, is used for advanced or widespread lung carcinoids. The choice of this kind of treatment is guided by several factors such as the grade of the tumor, the extent of the spread to other parts of the body, and individual patient characteristics.
What else can Lung Carcinoid Tumors be?
When doctors are diagnosing pulmonary carcinoids (a type of lung tumor), they also consider other conditions that might be causing the symptoms. These other possibilities include:
- Metastatic carcinoids (cancer that has spread) from other areas, especially the digestive tract
- Small cell lung carcinoma (another type of lung cancer)
- Tumors similar to those found in the salivary glands
- Metastases (cancer that has spread) of lobular breast carcinoma, paraganglioma, and glomangioma
- Tumorlets (small, benign tumors)
Surgical Treatment of Lung Carcinoid Tumors
Carcinoid tumors, a type of lung cancer, are usually treated through surgery. The aim of this procedure is to completely remove the tumor, and it’s the best method currently available to fully cure pulmonary carcinoids. The extent of the surgery will depend on the characteristics of the tumor, its location, and how advanced the disease is.
For early stage (stage I) pulmonary carcinoids, which are localized and still contained within the lung with no spread to the lymph nodes, doctors often opt for surgical resection with lobectomy, which is a surgery to remove a section (lobe) of the lung. Sometimes, in the case of tumors located centrally, complete removal of one lung (pneumonectomy) or of two lobes (bilobectomy) may be necessary. If the tumor is smaller and in the peripheral parts of the lung, a segmentectomy or wedge resection may be done; these are less extensive surgeries that focus on removing the tumor and some of the tissue around it.
Typical carcinoids, known to grow slowly and are localized with no lymph node involvement, can often be successfully treated with more limited surgeries. However, for atypical carcinoids that carry a higher risk of returning and spreading to other parts of the body, surgical guidelines for more aggressive forms of lung cancer are followed. Doctors often consider lobectomy for lesions smaller than 2 cm and remove lymph nodes in the chest region in all patients.
Whether or not to remove lymph nodes in the chest region during surgery for pulmonary carcinoids is a topic of discussion among medical professionals as there is limited evidence to suggest its benefits in reducing local recurrence and improving survival. However, it is widely recommended to remove them as it allows doctors to accurately determine the disease stage and guide subsequent decision making about further treatments.
Traditionally, a method called open thoracotomy, where a large incision is made in the chest, was used for removing parts of the lung. However, in recent years, a less invasive technique, video-assisted thoracic surgery (VATS), has become more popular and preferred. This technique results in less complications, shorter hospital stays, quicker recovery, and has shown to be beneficial both in the short and long term.
If an open thoracotomy is done, the technique has improved to allow for smaller, muscle-sparing incisions that result in less trauma to the chest and improved recovery after surgery.
Because most carcinoid tumors are located inside the bronchial tubes and usually grow quite slowly, doctors have been focusing on developing procedures that spare as much of the lung tissue as possible. Methods such as sleeve lobectomy and sleeve pneumonectomy have been performed successfully, allowing for excellent long-term outcomes.
What to expect with Lung Carcinoid Tumors
The chances of recovery from a type of lung cancer known as pulmonary carcinoids depend on a few things such as the size of the tumor, the tumor’s growth rate (known as grade), how far the disease has spread (disease stage), and the person’s age. The 5-year survival rate, which means the percentage of people who live at least 5 years after their cancer is diagnosed, varies depending on the stage of the disease. Generally, if the disease is caught earlier, the chances of living for at least 5 more years after diagnosis improves.
To give some numbers to this, the approximate 5-year survival rates for stages I to IV are 93%, 84%, 75%, and 57% respectively.
Also, there are two types of pulmonary carcinoids: typical and atypical. People diagnosed with typical carcinoids generally have better chances of living 5 years after diagnosis (about 90%) compared to those with atypical carcinoids (around 60%).
If the cancer has spread to the lymph nodes (known as nodal involvement), this is often seen as a sign that the disease might have a worse outcome. However, the effect of nodal involvement on disease outcome isn’t fully determined yet.
Other factors linked to a worse recovery chance in typical lung carcinoid tumors include incomplete removal of the tumor, the person’s age, gender, where the tumor is located (central versus peripheral), the TNM stage (which is a way to classify cancer’s size and spread), and how well the person can carry out daily living activities (performance status). A report in 2015 by a group of European lung surgeons showed that higher death rates were tied to things like older age, being male, having a tumor located in the periphery of the lung, a higher TNM stage, and having a lower ability to carry out daily activities.
Possible Complications When Diagnosed with Lung Carcinoid Tumors
Carcinoids are a type of tumor that can often impact the major bronchi of the lung. This may result in heavy and potentially life-threatening bleeding in the lungs.
However, complications such as carcinoid syndrome, Cushing syndrome, and acromegaly, are relatively rare. These conditions can occur if the tumor begins to produce abnormal peptides or hormones. This can lead to specific symptoms like frequent flushing, diarrhea, wheezing, and imbalances in hormone levels. [32] [33] It’s important to note that these effects are more commonly seen in gastrointestinal carcinoid tumors rather than those in the lungs.
People who smoke are at a higher risk of developing more primary lung cancers or other types of cancer related to smoking. While it’s not too common, receiving radiation treatment in the chest area can also increase the risk of developing secondary cancers and heart disease. Furthermore, other diseases related to smoking such as heart disease, stroke, and chronic obstructive pulmonary disease can also negatively affect survival.
Common Complications:
- Impact on major bronchi of the lungs
- Heavy and potentially life-threatening bleeding in the lungs
- Carcinoid syndrome, Cushing syndrome, and acromegaly
- Production of abnormal peptides or hormones
- Flushing, diarrhea, wheezing, hormone imbalances
- Increased risk of primary lung cancers or other smoking-related cancers
- Potential increase in risk of secondary cancers and heart disease due to chest irradiation
- Heart disease, stroke, and chronic obstructive pulmonary disease due to smoking
Preventing Lung Carcinoid Tumors
It’s important for patients to understand that there might be a chance of their disease coming back or spreading to other parts of the body. Regular check-ups, like those done for lung cancer patients after surgery, are crucial. These clinical follow-ups often include simple chest x-rays or CT scans every 2 to 3 months in the first year after surgery. After the first year, it’s advised that patients get checked once a year for the next 10 years.
Also, the current guidelines suggest that if a patient has a less aggressive type of cancerous tumor (known as a typical carcinoid tumor) and no cancer has been found in their lymph nodes, no further monitoring is needed. However, this is only the case if the tumor is less than 3 cm in size. If the tumor is bigger, or if there are cancer cells close to the cut edge of the tissue that was removed during surgery (close margins), or if there is cancer in more than one area, continued monitoring is recommended.
