Lung Cancer: Basic Info You Should Know

What Is Lung Cancer?

It’s cancer that starts in your lungs and can spread to other parts of your body. Although it’s the top cause of cancer deaths for U.S. men and women, it’s also one of the most preventable kinds, by not smoking and avoiding other people’s secondhand smoke.

Lung Cancer

The disease almost always starts in the spongy, pinkish gray walls of the lungs’ airways (called bronchi or bronchioles) or air sacs (called alveoli). There are more than 20 kinds. The two main types are non-small cell lung cancer and small-cell lung cancer. At first, you may not have any symptoms.

Non-Small Cell Lung Cancer

Adenocarcinoma is the most common kind of this. It makes up 40% of all lung cancer cases. It mainly happens in people who smoke (or who used to). And it’s also the No. 1 type of lung cancer among non-smokers.

More women get it than men. People with this type tend to be younger than those with other kinds. 

Adenocarcinoma can spread to the lymph nodes, bones, or other organs such as the liver.

Squamous cell carcinoma usually starts in the lung’s largest branches, which doctors call the “central bronchi.”    

This type accounts for 30% of lung cancers, and it’s more common in men and people who smoke. It may form a cavity within the tumor. It often involves the larger airways. It may make you cough up some blood.

Squamous cell carcinoma can also spread to the lymph nodes, bones, and other organs such as the liver. 

Large-cell carcinomas are a group of cancers with large cells that tend to start along the lungs’ outer edges. They're rarer than adenocarcinoma or squamous cell carcinoma, making up 10%-15% of lung cancers. This type of tumor can grow faster and often spreads to nearby lymph nodes and distant parts of the body.

Small Cell Lung Cancer

This is the most aggressive form of the disease. It usually starts in the lungs’ large, central bronchi. Almost all people who get it are smokers. It spreads quickly, often before symptoms appear. Many times, it spreads to the liver, bone, and brain.

The outlook for someone with lung cancer depends on a lot of things, including what type they have, their overall health, and how advanced the disease is when doctors find it.



Smoking is the biggest reason. It’s responsible for about 85% of all cases.

Quitting cuts the risk. Former smokers are still slightly more likely to get it than nonsmokers.

There are also other reasons. Some genetic glitches may put some people at higher risk. 

Secondhand tobacco smoke is also a cause. People who live with someone who smokes are 20% to 30% more likely to get lung cancer than those who live in a smoke-free home.

Some other chemicals are risky, too. People who work with asbestos or are exposed to uranium dust or the radioactive gas radon are more likely to get lung cancer, especially if they smoke.

Lung tissue that was scarred by a disease or infection, such as scleroderma or tuberculosis, becomes at risk for tumors in that tissue. Doctors call this a scar carcinoma.

Some researchers think that diet may also influence your risk. But that’s not clear yet.

WebMD Medical Reference Reviewed by Laura J. Martin, MD on July 11, 2018



National Cancer Institute. 

National Institutes of Health. 

WebMD Medical Reference from the American College of Physicians: “Section 12 VIII Lung Cancer.”

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