Small cell lung cancer is a rare and aggressive form of cancer that develops in the lungs and spreads rapidly throughout the body. While it accounts for only about 15% of all lung cancer cases, its fast-growing nature and tendency to metastasize early make it one of the most challenging types of cancer to manage. Understanding this disease, its causes, and how it affects the body can help patients and families navigate diagnosis and treatment with greater confidence.

How Common Is Small Cell Lung Cancer?

Small cell lung cancer represents a relatively uncommon form of lung cancer when compared to other types. In the United States, approximately 57 in every 100,000 people develop lung cancer each year, and small cell lung cancer makes up about 15% of those diagnoses^[1][2]. This means it is less common than non-small cell lung cancer, which accounts for roughly 85% of all lung cancer cases^[4].

The overall incidence of lung cancer, including small cell lung cancer, has been declining since the late 1980s. This decrease coincides with a reduction in smoking rates across the population^[4]. The relative incidence of small cell lung cancer specifically has decreased over the last four decades, reflecting not only lower smoking prevalence but also changes in cigarette manufacturing and reduced occupational hazards^[4].

Despite being less common than other forms of lung cancer, small cell lung cancer remains a significant health concern. Lung cancer as a whole is the second most diagnosed cancer in the United States and the leading cause of cancer death in both men and women, accounting for approximately a quarter of all cancer deaths^[4]. The aggressive nature of small cell lung cancer contributes to these sobering statistics.

What Causes Small Cell Lung Cancer?

The primary cause of small cell lung cancer is tobacco smoking. Smoking is responsible for approximately 85% to 98% of all small cell lung cancer cases, making it the most significant risk factor for this disease^[1][2][4]. People who smoke cigarettes, pipes, or cigars are at substantially increased risk. The relationship between smoking and small cell lung cancer is particularly strong compared to other types of lung cancer.

Cigarette smoke contains numerous harmful substances that can damage the cells in the lungs. These include polycyclic aromatic hydrocarbons, aromatic amines, N-nitrosamines, benzene, vinyl chloride, arsenic, and chromium, among many other carcinogens^[4]. When these chemicals are inhaled, they can cause cells in the lungs to mutate or change into cancerous cells that divide and multiply uncontrollably^[1].

There is a dose-dependent relationship between smoke exposure and the risk of developing lung cancer. This means that the amount you smoke, how deeply you inhale, how long you have been smoking, and whether your cigarettes have filters all influence your risk. The earlier in life a person starts smoking, the more often they smoke, and the more years they continue smoking, the greater their risk becomes^[4][5].

Beyond direct smoking, exposure to secondhand smoke also increases the risk of developing small cell lung cancer. Secondhand smoke refers to the smoke exhaled by smokers or emitted from burning tobacco products. People who live or work in environments where they regularly breathe in secondhand smoke face an elevated risk, even if they have never smoked themselves^[1][5].

Risk Factors That Increase Your Chances

While smoking is by far the most important risk factor, several other exposures and conditions can increase the likelihood of developing small cell lung cancer. Understanding these risk factors can help people make informed decisions about their health and environment.

Exposure to radon gas is a significant risk factor. Radon is a colorless, odorless radioactive gas that can seep into homes and other buildings from the ground. Long-term exposure to radon, particularly in combination with smoking, substantially increases lung cancer risk^[1][5].

Occupational exposures to certain hazardous substances also raise the risk. Workers who have been exposed to asbestos, arsenic, chromium, beryllium, nickel, soot, tar, or various toxic chemicals face higher rates of lung cancer^[1][5]. These workplace hazards can damage lung tissue over time, contributing to the development of cancer.

Previous radiation exposure can increase lung cancer risk. This includes radiation therapy to the breast or chest, imaging tests such as computed tomography scans, atomic bomb radiation, and radiation from other sources^[1][5]. While medical imaging is often necessary and beneficial, cumulative radiation exposure over a lifetime may contribute to cancer risk.

Having a family history of lung cancer increases the risk of developing the disease. Genetic factors can make some people more susceptible to lung cancer, even if they have not been exposed to tobacco smoke^[1][5]. Additionally, people infected with the human immunodeficiency virus (HIV) have an elevated risk of lung cancer^[1][5].

Living in areas with high levels of air pollution may also contribute to lung cancer risk^[5]. Older age is the main risk factor for most cancers, including lung cancer. As people get older, their cells accumulate more damage over time, which can lead to cancer^[5].

When smoking is combined with other risk factors such as radon exposure or occupational hazards, the risk of lung cancer increases even more dramatically. This multiplicative effect means that people who smoke and are also exposed to other carcinogens face particularly high risks.

Recognizing the Signs and Symptoms

One of the challenges with small cell lung cancer is that it often does not cause noticeable symptoms in its early stages, especially when it has not yet spread beyond the lung. Nearly 25% of lung cancer cases produce no symptoms at all^[2]. When symptoms do appear, they can be similar to those caused by other, less serious respiratory conditions, which can delay diagnosis.

A persistent cough that does not go away or worsens over time is one of the most common symptoms. This chronic cough may be different from the usual smoker’s cough or may develop in someone who has recently quit smoking^[1][2][5]. Some people may cough up blood, a condition known as hemoptysis, which should always be evaluated by a healthcare provider^[1][5].

Chest pain or discomfort is another warning sign. This pain may be dull, aching, or sharp, and it can worsen with deep breathing, coughing, or laughing^[1][2][5]. Difficulty breathing or shortness of breath, known medically as dyspnea, occurs when the tumor obstructs airways or when fluid builds up around the lungs^[1][2][5].

Wheezing, which is a high-pitched whistling sound during breathing, can occur when airways become narrowed or blocked^[1][2][5]. Hoarseness or changes in the voice may develop if the cancer affects the nerves that control the voice box^[1][2][5].

Systemic symptoms, which affect the whole body, include fatigue, loss of appetite, and unexplained weight loss^[1][2][5]. These symptoms occur because cancer can alter metabolism and energy use throughout the body.

In some cases, small cell lung cancer causes swelling in the face and neck. This happens when the tumor compresses the superior vena cava, a large vein that carries blood from the upper body to the heart. This compression can lead to facial swelling and distension of the neck veins^[1]. Trouble swallowing may occur if the tumor compresses the esophagus, the tube that carries food from the mouth to the stomach^[2].

Because small cell lung cancer often spreads early to other parts of the body, symptoms may also arise from metastases in distant organs. When cancer spreads to the bones, it can cause bone pain. If it spreads to the brain, it may cause seizures, confusion, paralysis, or personality changes. Metastases to the liver or adrenal glands can cause abdominal pain or other symptoms^[2].

Many of these symptoms can be caused by conditions other than cancer. However, if you smoke or used to smoke and notice any of these symptoms, especially if they persist or worsen, it is important to talk to a healthcare provider. Early evaluation can lead to earlier diagnosis and treatment, which may improve outcomes.

Preventing Small Cell Lung Cancer

The most effective and proven way to prevent small cell lung cancer is to avoid smoking tobacco. Because smoking is responsible for the vast majority of small cell lung cancer cases, never starting to smoke or quitting smoking are the most powerful preventive actions anyone can take^[1].

For people who currently smoke, quitting at any age can reduce the risk of developing lung cancer. Even individuals who have smoked for many years can benefit from quitting. The body begins to repair some of the damage caused by smoking soon after cessation, and the risk of lung cancer decreases over time. The earlier in life you quit, the greater the reduction in risk, but quitting at any age is beneficial.

Avoiding exposure to secondhand smoke is also important. If you live or work with people who smoke, encourage them to smoke outdoors and away from others. Policies that prohibit smoking in public places, workplaces, and homes help protect non-smokers from the harmful effects of secondhand smoke^[1][5].

Reducing exposure to radon gas is another preventive measure. Homeowners can have their homes tested for radon, and if levels are elevated, mitigation systems can be installed to reduce radon concentrations. Radon testing kits are widely available and relatively inexpensive^[1][5].

For people who work in occupations with potential exposure to carcinogens such as asbestos, arsenic, or other hazardous substances, following workplace safety guidelines and using protective equipment can help reduce risk. Employers are required to provide safety measures and training to minimize workers’ exposure to harmful substances^[1][5].

While no lifestyle change can guarantee the prevention of lung cancer, reducing or eliminating known risk factors is the best strategy for lowering your chances of developing this disease.

How Small Cell Lung Cancer Affects Your Body

Small cell lung cancer begins when healthy cells in the lungs undergo changes, or mutations, that transform them into cancerous cells. Once these cells become cancerous, they start to divide and multiply uncontrollably. Unlike normal cells, which have mechanisms to stop growing when necessary, cancer cells continue to reproduce without regulation^[1].

As the cancerous cells multiply, they clump together to form masses called tumors in the lungs. These tumors usually start in the airways of the lung, often in the bronchi, which are the large tubes that branch off from the trachea (windpipe) into the lungs^[2][6].

Small cell lung cancer is particularly aggressive because it grows and spreads rapidly. The tumors can shed cancer cells that enter the bloodstream or the lymphatic system. Lymph is a fluid that circulates through the body, carrying immune cells and waste products through a network of vessels and nodes^[1]. When cancer cells enter the blood or lymph, they can travel to distant parts of the body.

Small cell lung cancer typically spreads to the lymph nodes first, particularly those in the chest. From there, it commonly metastasizes to the bones, brain, liver, and adrenal glands, which are small glands located near the kidneys^[1][2]. Once cancer cells reach these distant sites, they can form new tumors, causing additional symptoms and complications.

In 60% of small cell lung cancer cases, the cancer has already metastasized to other areas of the body by the time it is diagnosed. This early and widespread metastasis is one of the reasons small cell lung cancer is so difficult to treat^[2][7].

Small cell lung cancer can also cause fluid to accumulate in the lungs or in the space around the lungs, a condition called pleural effusion. This fluid buildup can make it difficult to breathe and may cause the lung to collapse by pushing air out^[1].

The cancer may also cause compression of structures in the chest. For example, it can compress the superior vena cava, leading to facial swelling and swollen neck veins. It can press on the esophagus, causing difficulty swallowing, or on nerves, leading to hoarseness or other neurological symptoms.

There are two main types of small cell lung cancer. Small cell carcinoma, also known as oat cell cancer, is the most common form^[1][5][6]. The second type is combined small cell carcinoma, which is a rare subtype that has characteristics of both small cell and non-small cell lung cancer within the same tumor. Combined small cell carcinoma represents about 2% to 5% of all small cell lung cancer cases^[1][6].