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, mostly among smokers. A growing number of cases are being found in people who never smoked, which means factors like the environment or genetics may be involved.

Lung cancer is considered either nonsmall cell or small cell, which describes how the cells look when viewed under a microscope.


What Are the Types of Lung Cancer?

There are three main kinds of lung cancer — small cell, nonsmall cell and carcinoid lung tumors. Of these, nonsmall cell is by far the most common, while small cell lung cancer, which tends to spread quickly, is found in 10 to 15 percent of cases. Fewer than 5 percent of lung cancers are lung carcinoid tumors.

Nonsmall Cell Lung Cancer

Nonsmall cell lung cancers are the most common types of lung cancer, accounting for approximately 80 to 85 percent of lung cancer cases. Nonsmall cell lung cancer can form in different parts of the lungs, and can spread to other parts of the body as the cancer develops.
Types of nonsmall cell lung cancer include:
  • Adenocarcinoma is the most common type of nonsmall cell lung cancer; it begins in the deepest parts of the breathing passages, called the 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, that tends to grow and spread quickly. It can begin in any part of the lungs.
  • Other types of disease called adenosquamous carcinoma and sarcomatoid carcinoma are rare types of nonsmall cell lung cancer.

Small Cell Lung Cancer

Small cell lung cancer is sometimes called oat cell lung cancer, because the small, oval-shaped cancer cells resemble oats when viewed under a microscope. It is an aggressive cancer, most common in smokers, that tends to grow fast and spread quickly to other parts of the body. About 10 to 15 percent of all lung cancers are small cell cancers.

Pulmonary Metastases

Cancer that comes from another part of the body to the lungs is called pulmonary metastasis. These cancer types are defined by the organ in which they started, and are not technically lung cancer. For example, breast cancer cells that travel to the lungs are considered breast cancer that has metastasized (spread) to the lungs.

Some common cancers that spread to the lungs include bladder cancer, breast cancer, colon cancer, kidney cancer, melanoma, ovarian cancer, thyroid cancer and sarcoma.

Pulmonary Neuroendocrine Tumors

Neuroendocrine tumors form from endocrine cells, which are scattered throughout the body and release hormones into the blood in response to signals from the nervous system. Such tumors can form in various parts of the body, including the lungs.

Pulmonary neuroendocrine tumors include:

  • Large cell neuroendocrine carcinoma. This subtype of nonsmall cell lung cancer is rare and tends to grow quickly.
  • Typical carcinoid tumor. These tumors tend to grow slowly and rarely spread beyond the lungs.
  • Atypical carcinoid tumor. About 10 percent of carcinoid tumors are atypical. They more closely resemble fast-growing tumors and are somewhat more likely to spread than typical carcinoid tumors.

How Lung Cancer Develops

Lung tissue is some of the most sensitive in the body, and its health is largely affected by what you breathe in. Inhaling things like cigarette smoke, air pollution or the fumes from other substances like certain household products — along with certain genetic factors — may lead to harmful changes to cells in your lungs.

Getting Lung Cancer

Your 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 through a large tube called the trachea, then branches out through a network of smaller tubes in the lungs called the bronchi and bronchioles — and finally ends up inflating tiny air sacs called alveoli.

Getting lung cancer means abnormal cells in your lungs are growing and dividing at a rapid pace — so fast that cells in your immune system that fight disease cannot keep up.

Besides damaging lung tissue, clusters of those abnormal cells — called tumors — can block your airways, causing problems like cough, chest pain and sometimes bleeding.

If it is caught early, lung cancer may be treated with surgery. In more advanced cases, cancer cells will have spread from one lung to another or moved to other parts of the body — a process called metastasis. Lung cancer that has metastasized tends to go to the adrenal gland, bones, brain or liver.

Some first steps for finding lung cancer involve your doctors identifying any signs and symptoms you are experiencing; performing screening tests to identify whether they are due to lung cancer — and finding out whether the disease has spread.

What Increases Your Risk of Lung Cancer?

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

Risk Factors for Lung Cancer

  • Smoking cigarettes is responsible for between 80 to 90 percent of lung cancer deaths in men and women — and the more you smoke the higher your risk. Just being around cigarette smoke also can affect your risk: Being exposed to secondhand smoke at home or work increases the chances of lung cancer by 20 to 30 percent.
  • Being exposed to radon is the second leading cause of lung cancer. It occurs naturally in soil, water and rock and can be found in homes, buildings and schools.
  • Tiny fibers of asbestos can be breathed in and become lodged in lung tissue. Until a few decades ago, asbestos was a common ingredient in things like building materials, steam pipes, vehicle brake shoes and plastics. Asbestos was banned as a new material decades ago, but still is present in the environment.
  • Exposure to materials like uranium, arsenic, vinyl chloride, coal products, mustard gas, diesel exhaust and others may increase your risk of lung cancer.
  • Breathing in air pollution like diesel engine exhaust, metals, dust and solvents — found in products like paint, personal care products, nail polish remover and household cleaners — may increase your risk for lung cancer.
  • Having a family history, like parents or siblings with lung cancer, increases your risk.
  • Older age makes you more likely to get cancer. Close to 90 percent of people diagnosed with lung cancer are 55 or older.
  • Other lung diseases like COPD (chronic obstructive pulmonary disease) or pulmonary fibrosis increase your risk of getting lung cancer.

Having some combination of exposures, like being a smoker who also was exposed to asbestos, may increase your chances of getting lung cancer.


The best way to reduce your risk for lung cancer is to stop smoking. Other things like testing your home for radon and avoiding secondhand smoke also may help. Exercising and eating a healthy diet also may reduce your risk of lung cancer.

Are You a Smoker?

Do you know what's in cigarette smoke? Find out by watching the video below.

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If you are a current or former smoker, you may reduce your risk of dying of lung cancer by getting screened for lung cancer with a low dose radiation computed tomography scan of your lungs. Lung cancer screening is safe, painless and saves lives. And research shows that chemotherapy works more effectively, and there are fewer complications from surgery, in nonsmokers.

What Are the Signs and Symptoms of Lung Cancer?

Most lung cancers do not cause symptoms until they have grown very large or have spread. That is when symptoms like cough, chest pain and breathing problems come on and do not go away. It also may be found during a chest X-ray or a screening test for some other condition.         

Later Lung Cancer Symptoms

Once lung cancer has progressed, your symptoms may be different since later-stage cancer affects 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 could mean lung cancer or they might be a completely different issue. It is important to get screened to find out if these symptoms are because of cancer or some other medical problem.