Lung Cancer Facts

What Is Lung Cancer?

Lung cancer is the most common type of cancer worldwide. Around 240,000 new cases of lung cancer will be diagnosed in the United States this year alone, mostly among smokers. More and more cases are being found among people who never smoked, which suggests that factors like the environment or genetics may also be involved in the development of lung cancer.

Types of Lung Cancer

The three main lung cancer types are nonsmall cell lung cancer (NSCLC), small cell lung cancer and carcinoid lung tumors. NSCLC is by far the most common of these three. Small cell lung cancer, which tends to spread quickly, is found in 10-15% of cases. Fewer than 5% of lung cancers are carcinoid lung tumors.

Nonsmall Cell Lung Cancer

NSCLC is the most common kind of lung cancer, accounting for around 80-85% of all cases. NSCLC can form in different parts of the lungs and may spread to other parts of the body as it develops.

There are several types of NSCLC:

  • Adenocarcinoma is the most common. It begins in the deepest parts of the breathing passages, or alveoli. This type of lung cancer is most common in people who have never smoked.
  • Squamous cell carcinoma starts in the flat, thin cells lining the inside of the airways. It tends to develop in the bronchi, near the middle of the lungs.
  • Large cell carcinoma is an aggressive type of lung cancer with large, abnormal looking cells. It tends to grow and spread quickly. It can begin in any part of the lungs.
  • Other rare types of NSCLC include adenosquamous carcinoma and sarcomatoid carcinoma.

Small Cell Lung Cancer

Small cell lung cancer — sometimes called oat cell lung cancer because of the cell’s shape — is an aggressive cancer that is most common in smokers. It tends to grow fast and spread quickly. About 10-15% of all lung cancers are small cell cancers.

Carcinoid Lung Tumors  

Carcinoid lung tumors are a rare type of cancer that accounts for less than 5% of all lung cancer diagnoses. Most kinds of carcinoid lung tumors are referred to as “typical,” meaning they grow slowly and can often be treated with surgery. However, there are also “atypical” carcinoid lung tumors that grow faster. Carcinoid lung tumors are a type of pulmonary neuroendocrine tumor.

Pulmonary metastasis refers to cancers that originated in another part of the body but have spread, or metastasized, to the lungs. These cancer types are still defined by the organ in which they started, for example, breast cancer cells that travel to the lungs are considered breast cancer that has metastasized to the lungs. 

Stages of Lung Cancer

After receiving a lung cancer diagnosis, doctors will usually recommend tests to help understand what stage the cancer is at. The results of these tests also help determine the best treatment options to pursue. 

NSCLC and small cell lung cancer are staged differently.

The Stages of Lung Cancer
The Stages of NSCLC
Basic Text Field
  • Stage 0: At this point, the cancer is confined to the top lining of the lung or bronchus.
  • Stage 1: This stage is divided into 1A and 1B, depending on the size of the tumor. The cancer has not spread to the lymph nodes or other parts of the body.
  • Stage 2: This stage is divided into 2A and 2B. These substages reflect how big the tumor is and whether it has begun to spread to the lymph nodes. It has not spread to distant parts of the body.
  • Stage 3: In stages 3A, 3B or 3C, the cancer may be larger or have spread further. Most often, it has spread to the lymph nodes between the lungs.
  • Stage 4: This is the most advanced stage of lung cancer. At Stage 4, the cancer has spread to the lining of the lungs or other parts of the body.
The Stages of Small Cell Lung Cancer
Basic Text Field
  • Limited stage: The cancer is confined to one lung and has not spread to the lymph nodes in the chest.
  • Extensive stage: The cancer has spread to the other lung or to other sites in the body.

How Lung Cancer Develops

The lungs are a tree-like series of connected tubes surrounded by thick, spongy lobes. There are three lobes in the right lung and two on the left (to make space for the heart). When you breathe in, air travels down a large tube called the trachea, then branches out through a network of smaller tubes in the lungs called the bronchi and bronchioles. Finally, it ends up inflating tiny air sacs called alveoli. Lung tissue is some of the most sensitive in the body, and its health is largely affected by what we breathe in.  

Lung cancer develops when abnormal cells in your lungs grow and divide at a rapid pace — so fast that the cells in your immune system that fight disease cannot keep up. These clusters of abnormal cells are called tumors. They can damage lung tissue and block your airways, causing issues like coughs, chest pain or bleeding. 

If it is caught early, lung cancer may be treated with surgery, including advanced lung-sparing surgery available at City of Hope. In more advanced cases, cancer cells spread from one lung to another or move to other parts of the body, such as the adrenal gland, bones, brain or liver.

If you experience any symptoms of lung cancer, it is important to make an appointment with a specialist.

Lung Cancer Risk Factors

Things that put you at higher risk of getting lung cancer are called risk factors. Most people who get lung cancer are smokers, but around 20% of lung cancer cases occur in nonsmokers.

  • Smoking cigarettes is responsible for 80-90% of lung cancer deaths in men and women. The more you smoke, the higher the risk of getting lung cancer. This is because cigarette smoke includes harmful substances, such as nicotine, carbon monoxide and other dangerous chemicals. Being exposed to secondhand smoke also increases the chances of lung cancer by 20-30%.
  • Being exposed to radon is the second-leading cause of lung cancer. Radon occurs naturally. It can be found in soil, as well as buildings.
  • Tiny fibers of asbestos can be breathed in and become lodged in lung tissue. Though asbestos is now banned, it is still commonly found in buildings and our environment.
  • Exposure to certain materials, like cadmium, uranium, arsenic, vinyl chloride or coal may increase your risk.
  • Breathing in air pollution like diesel exhaust, dust or solvents may increase your risk for lung cancer.
  • Having a family history of lung cancer, for instance, parents or siblings with the disease, can increase your risk.
  • Older age makes you more likely to get cancer. Close to 90% of people diagnosed with lung cancer are 55 or older.
  • Having another lung disease, such as COPD (chronic obstructive pulmonary disease), increases your risk of getting lung cancer.

Exposure to more than one risk factor can also increase your overall chances of getting lung cancer.

Lung Cancer Prevention

The best way to reduce your risk of developing lung cancer is to stop smoking. Research also shows that chemotherapy works more effectively for nonsmokers, and that they experience fewer complications from surgery. Other preventive steps include:

  • Testing your home for radon.
  • Avoiding secondhand smoke.
  • Exercising regularly.
  • Maintaining a healthy diet. 

If you used to be a smoker, or if you still smoke, you may reduce your risk of dying of lung cancer by getting screened for the disease. This is done using a low-dose radiation computed tomography scan of your lungs. Lung cancer screening is safe, painless and saves lives. 

What Are the Symptoms of Lung Cancer?

Most lung cancers do not cause symptoms until they have grown very large or have spread. At that point, common symptoms, such as a cough, chest pain or breathing problems, may be frequent or never go away. Cancer is sometimes detected during a chest X-ray or when screening for another condition.         

Later Lung Cancer Symptoms

When lung cancer has progressed, your symptoms may be different. This is because later-stage cancer can affect other parts of the body, like the brain or bones. Later-stage lung cancer symptoms may include:

  • Drooping eyelids
  • Pain or tenderness in your bones or joints
  • Bone fractures
  • Facial paralysis
  • Changes to your voice, like hoarseness
  • Difficulty swallowing
  • Shoulder pain
  • Weakness
  • Nail problems
  • Swelling in your face or arms

These symptoms can indicate lung cancer, but they may also be related to a different issue. Getting screened for lung cancer is the best way to ensure you get the care you need.