Understanding Lung Carcinoid Tumors: A Comprehensive Patient Guide

Table of Contents

• What Are Lung Carcinoid Tumors?
• Causes and Risk Factors
• Who Gets Lung Carcinoid Tumors?
• Symptoms and Presentation
• Diagnostic Process
• Treatment Options
• Outlook and Survival Rates
• Potential Complications
• Long-Term Monitoring
• Source Information

What Are Lung Carcinoid Tumors?

Lung carcinoid tumors are uncommon neuroendocrine malignancies that develop from specialized cells in the lungs. These rare tumors represent less than 1% of all lung cancers, making them significantly less common than other lung cancer types. Unlike most lung cancers, carcinoid tumors are not associated with smoking and tend to grow more slowly.

Doctors classify pulmonary carcinoids into two main categories based on their microscopic appearance and behavior. Typical carcinoids are low-grade tumors with less than 2 cell divisions (mitoses) per 2 mm² and no tissue death (necrosis). Atypical carcinoids are intermediate-grade tumors with 2-10 mitoses per 2 mm² and areas of necrosis. Typical carcinoids make up 85-90% of cases, while atypical carcinoids account for the remaining 10-15%.

These tumors show distinct patterns in where they develop within the lungs. Approximately 80% occur centrally near the main airways, while 20% develop in the peripheral areas of the lungs. Despite their generally slow growth, all bronchial carcinoids are considered malignant and have the potential to spread to other parts of the body.

Causes and Risk Factors

The exact causes of lung carcinoid tumors remain unclear, and researchers continue to study what triggers their development. While smoking doesn't appear to be a direct cause as with other lung cancers, some evidence suggests that more patients with atypical carcinoids are smokers compared to those with typical carcinoids.

Certain environmental factors may contribute to risk. Some studies have identified specific air pollutants and chemicals as potential risk factors, though more research is needed to confirm these relationships. In rare cases, lung carcinoids can occur in association with multiple endocrine neoplasia type 1 (MEN-1) syndrome, a genetic condition that affects hormone-producing glands.

Researchers have found that even in non-inherited cases, the MEN-1 gene sometimes shows changes (inactivation), suggesting a potential genetic component to these tumors' development. This genetic connection helps explain why these tumors can sometimes run in families, though most cases occur without any family history.

Who Gets Lung Carcinoid Tumors?

Lung carcinoid tumors can affect people across a wide age range, from as young as 5 years to as old as 90 years. The average age at diagnosis is approximately 50 years, with atypical carcinoids typically appearing about 10 years earlier than typical carcinoids. Notably, about 8% of these tumors are diagnosed during the teenage years (second decade of life), making them the most common primary pulmonary tumor in childhood.

Research shows some demographic patterns in who develops these tumors. Data suggests a higher incidence among white individuals compared to other ethnic groups. Women appear slightly more likely to develop these tumors than men, though the difference isn't dramatic.

Over recent decades, doctors have observed an increasing incidence of carcinoid tumors, including those in the lungs. This upward trend likely reflects improved detection methods through advanced imaging technologies rather than an actual increase in cases. Better awareness and diagnostic tools mean these tumors are being identified more frequently than in the past.

Symptoms and Presentation

Approximately 25% of people with lung carcinoid tumors experience no noticeable symptoms at all. These tumors are often discovered incidentally during medical tests or imaging performed for unrelated health concerns. When symptoms do occur, they typically relate to the tumor's location and size.

The most common symptoms include:

• Persistent coughing or wheezing
• Hemoptysis (coughing up blood)
• Symptoms related to lung collapse or pneumonia developing beyond blocked airways
• Stridor (a high-pitched breathing sound) in some cases

Since these are neuroendocrine tumors, some patients may develop carcinoid syndrome, though this occurs in less than 3% of cases. Symptoms of carcinoid syndrome include:

• Facial flushing (redness and warmth)
• Shortness of breath
• High blood pressure
• Unexplained weight gain
• Excessive hair growth (hirsutism)
• Asthma-like symptoms

Most pulmonary carcinoid tumors are "endocrinologically silent," meaning they don't produce significant amounts of hormones that cause noticeable symptoms. When hormone-related syndromes do occur, they can include carcinoid syndrome, Cushing syndrome (from cortisol overproduction), and acromegaly (from growth hormone excess).

Diagnostic Process

Diagnosing lung carcinoid tumors involves multiple approaches to confirm the diagnosis and determine the extent of disease. The process typically begins with blood tests including plasma chromogranin A measurement, complete blood count, electrolyte levels, and liver and kidney function tests. These help establish a baseline and check for hormone production.

When symptoms suggest hormonal secretion, doctors order specific tests:

• Urinary 5-hydroxy indoleacetic acid (5-HIAA) to detect serotonin metabolism
• Serum cortisol and 24-hour urine free cortisol levels for Cushing syndrome
• Adrenocorticotropic hormone (ACTH) levels for suspected Cushing's disease
• Growth hormone-releasing hormone (GHRH) and insulin growth factor (IGF)-I levels for acromegaly

Bronchoscopy plays a crucial role in diagnosis since most tumors are centrally located and visible during this procedure. During bronchoscopy, doctors can directly visualize the tumor and obtain tissue samples (biopsies). However, this procedure carries a risk of bleeding due to the highly vascular nature of these tumors.

Imaging studies provide essential information about the tumor's characteristics and location. Standard chest X-rays detect these tumors in about 40% of cases. Computed tomography (CT) scans with intravenous contrast represent the gold standard for radiological evaluation, typically showing well-defined, round masses that may be slightly lobulated.

Advanced imaging techniques help distinguish carcinoid tumors from other cancers:

• FDG PET scans help differentiate carcinoids from high-grade neuroendocrine tumors
• Octreotide SPECT and gallium-labeled somatostatin analogs improve detection sensitivity
• Indium-111-labeled-octreotide imaging enhances diagnosis, staging, and recurrence monitoring

Treatment Options

Surgical resection remains the primary treatment for lung carcinoid tumors and offers the best chance for cure. The extent of surgery depends on several factors including tumor type (typical vs. atypical), location, size, and whether the tumor has spread to lymph nodes.

For typical carcinoids without lymph node involvement, limited resections such as wedge resection or segmentectomy may be sufficient. Lobectomy (removal of an entire lung lobe) is commonly performed, especially for larger tumors or those located centrally. In cases where tumors involve major airways, surgeons may perform bronchoplastic procedures to preserve lung function while completely removing the tumor.

Video-assisted thoracic surgery (VATS) has become the preferred surgical approach due to its benefits including reduced morbidity, shorter hospital stays, and faster recovery compared to traditional open thoracotomy. Studies have demonstrated excellent short-term and long-term outcomes with VATS, making it the standard approach where technically feasible.

The role of additional treatments after surgery (adjuvant therapy) remains debated. The National Comprehensive Cancer Network guidelines recommend considering adjuvant cisplatin and etoposide chemotherapy with or without radiation for stage III atypical carcinoids. The European Neuroendocrine Tumor Society similarly advocates adjuvant treatment for atypical carcinoids with positive lymph nodes but not for typical carcinoids.

For advanced or metastatic disease, treatment options include:

• Somatostatin analogs to control symptoms and slow progression
• Chemotherapy regimens (cisplatin/etoposide or temozolomide/capecitabine)
• mTOR inhibitors like everolimus, which showed 9.6 months progression-free survival vs. 3.6 months with placebo
• Anti-VEGF agents that target blood vessel formation

Outlook and Survival Rates

The prognosis for lung carcinoid tumors depends on several factors including tumor type, stage at diagnosis, patient age, and completeness of surgical removal. Overall, these tumors have better outcomes than most other lung cancers, particularly when detected early.

Five-year survival rates vary significantly by stage:

• Stage I: 93% survival rate
• Stage II: 84% survival rate
• Stage III: 75% survival rate
• Stage IV: 57% survival rate

Tumor type dramatically affects outcomes. Typical carcinoids have an excellent prognosis with approximately 90% five-year survival, while atypical carcinoids show around 60% five-year survival. The presence of cancer in lymph nodes represents a poor prognostic factor, though the exact impact continues to be studied.

Additional factors associated with poorer outcomes include incomplete surgical removal, older age, male gender, peripheral tumor location (versus central), advanced TNM stage, and poorer overall health status. A 2015 European study confirmed that increased age, male gender, peripheral location, higher stage, and lower functional status all correlated with higher mortality.

Potential Complications

Lung carcinoid tumors can lead to several serious complications, primarily related to their location and biological behavior. Since these tumors often develop in major airways, they can cause massive, life-threatening hemoptysis (bleeding from the respiratory tract) that requires emergency medical attention.

Although rare (occurring in less than 3% of cases), hormone-related syndromes represent significant complications:

• Carcinoid syndrome: flushing, diarrhea, wheezing due to serotonin secretion
• Cushing syndrome: weight gain, high blood pressure, diabetes from cortisol excess
• Acromegaly: enlarged hands, feet, and facial features from growth hormone overproduction

Patients who smoke face additional risks including increased chance of developing second primary lung cancers or other smoking-related malignancies. Those who receive chest radiation therapy (though rarely used) have elevated risks of secondary cancers and coronary artery disease. Other tobacco-related conditions like cardiovascular disease, stroke, and COPD can further impact survival and quality of life.

Long-Term Monitoring

After treatment, patients require careful long-term monitoring for potential recurrence or metastasis. Follow-up protocols generally resemble those for other lung cancers, with clinical evaluations and imaging studies at regular intervals. Typically, patients undergo clinical check-ups and chest X-rays or CT scans every 2-3 months during the first year after surgery.

After the first year, annual follow-up is recommended for up to 10 years. However, current guidelines suggest that node-negative typical carcinoid tumors smaller than 3 cm with clear surgical margins and no multifocal disease may not require intensive surveillance. The need for ongoing monitoring depends on individual factors including tumor characteristics, treatment response, and overall health status.

The healthcare team plays a crucial role in long-term management. Due to the non-specific symptoms of these tumors, coordination between pulmonologists, radiologists, pathologists, medical oncologists, and thoracic surgeons ensures comprehensive care. This multidisciplinary approach helps address any complications, manage side effects of treatment, and promptly identify any signs of recurrence.

Source Information

Original Article Title: Lung Carcinoid Tumors - StatPearls - NCBI Bookshelf

Authors: Faten Limaiem, Muhammad Ali Tariq, Uzma Ismail, Jason M. Wallen

Affiliations: University of Tunis El Manar, Tunis Faculty of Medicine; Tower Health; Specialist Care Clinic; Upstate Medical University

Publication Details: StatPearls Publishing; 2025 Jan-

Last Update: June 15, 2023

This patient-friendly article is based on peer-reviewed research from the National Center for Biotechnology Information (NCBI) Bookshelf.