An Overview of Lung Cancer

Lung cancer is the leading cause of cancer deaths worldwide, with 1.8 million new cases being diagnosed yearly.

In the United States, lung cancer is the most fatal cancer in women, having passed breast cancer in 1987 as the leading cause of cancer-related deaths. It is also the most fatal cancer in men, killing more men than prostate cancer, pancreatic cancer, and colon cancer combined. Overall, 27 percent of cancer deaths in the U.S. are due to lung cancer.


Before anyone dismisses these numbers as due to smoking alone, it's important to point out that even if smoking were banned today, we would still have lung cancer. Lung cancer in never-smokers is the sixth leading cause of cancer deaths in the United States. In fact, the focus on smoking cessation as a way to treat lung cancer has, in some ways, overshadowed research looking into other causes.

What Is Lung Cancer?

Lung cancer originates in the tissues of the lungs or the cells lining the airways (the bronchi).

 These cells begin as and look like lung cancer cells under the microscope, with the exception of changes that occur in the process of becoming cancerous.

If lung cancer spreads to other regions of the body, the cells are still lung cancer cells. For example, if lung cancer spreads to the brain, cells taken from the metastasis (growth) in the brain would be identifiable as cancerous lung cancer cells under the microscope. In contrast, some tumors begin in other parts of the body and spread (metastasize) to the lungs. This is referred to as metastatic cancer to the lungs and not lung cancer. An example would be a breast cancer which spreads to the lungs.

This would not be called lung cancer, but rather "breast cancer metastatic to the lungs."  

Anatomy of Lung Cancer

Lung cancer may occur anywhere in the lungs. The right lung is made up of three lobes and the left lung, two lobes.

When we take a breath of air, it enters through our nose and mouth, passes down through the trachea (the windpipe) and then into the mainstem bronchus. It then travels via a bronchus to either the right or the left lung. Once in the bronchi, the air then travels through increasingly smaller bronchioles and on into the alveoli—tiny air sacs in the lungs through which the exchange of carbon dioxide and oxygen takes place. Capillaries (the smallest of blood vessels) surround the alveoli, receiving the oxygen to carry it to the rest of the body. Cancer may occur anywhere in the respiratory system from the large bronchi down to the alveoli.

Where Is Lung Cancer Most Common?

Unfortunately, lung cancer is common throughout the world. Overall, the countries with the most lung cancer worldwide include Hungary, Serbia, and Korea.

Looking at lung cancer in women, however, the highest incidence is found in Denmark, followed closely by Canada and then the United States.

Who Gets Lung Cancer?

The average age for lung cancer is 70, and 80 percent of people who develop lung cancer have smoked, but:

Lung cancer occurs in women - Women are actually much more likely to die from lung cancer than breast cancer, and the incidence of lung cancer in women has almost caught up with that in men. In 2016 it's estimated that 85,920 men and 72,160 women will die from lung cancer. In comparison, 40,450 women will die from breast cancer.

Lung cancer occurs in non-smokers  - And while lung cancer in men who have smoked is decreasing, lung cancer in non-smokers is increasing. It's estimated that 20 percent of women who develop lung cancer in the U.S. have never smoked, and that number increases to 50 percent worldwide.

Lung cancer occurs in young adults - It's estimated that 13.4 percent of lung cancers occur in adults under the age of 40.

While this number may seem small, when compared to the incidence of lung cancer overall, it is not. Calculating this out, around 21,000 young adults will die from lung cancer this year (again comparing this to 40,450 breast cancer deaths for women of all ages.) In addition, women are more likely than men to develop lung cancer at a young age, and lung cancer in young adults is increasing.

Types of Lung Cancer

There are two primary types of lung cancer:

  • Non-small cell lung cancer is most common, being responsible for 80 to 85 percent of cancers.  This is the type of lung cancer more commonly found in non-smokers, women, and young adults.
  • Small cell lung cancer is responsible for around 15 percent of lung cancers. These lung cancers tend to be aggressive and may not be found until they have already spread (especially to the brain). They usually respond fairly well to chemotherapy but have a poor prognosis. 

Non-small cell lung cancer is further broken down into three types:

  • Lung adenocarcinoma - Lung adenocarcinoma is responsible for half of non-small cell lung cancers and is currently the most common type of lung cancer. It is also the most common type of lung cancer found in women, young adults, and in people who do not smoke.
  • Squamous cell carcinoma of the lungs - Squamous cell lung cancer was once the most common type of lung cancer, but its incidence has decreased in recent years. Part of the thought is that the addition of filters to cigarettes created this shift. Squamous cell cancers tend to occur in or near the large airways - the first place exposed to smoke from a cigarette. Lung adenocarcinomas, in contrast, are usually found deeper in the lungs, where smoke from a filtered cigarette would settle.
  • Large cell lung cancer - Large cell carcinomas of the lungs tend to grow in the outer regions of the lungs. These are usually rapidly growing tumors that spread quickly.

Other, less common types of lung cancer include carcinoid tumors and neuroendocrine tumors.

Signs and Symptoms of Lung Cancer

Having an awareness of the early signs and symptoms of lung cancer is a must for everyone for two reasons:

  • There is not a screening test available for everyone, so the only way that most people have to find these cancers early—when  they are most treatable—is knowing the signs. Recent research tells us that the majority of people in the United States are not familiar with these symptoms.
  • Because lung cancer is common. As noted earlier, lung cancer is the leading cause of death in both men and women and anyone who has lungs is at risk.

Overall, the most common symptoms include:

  • shortness of breath with activity
  • a persistent cough
  • coughing up blood
  • unexplained weight loss
  • chest pain

Of note is that the types of lung cancer have been changing over the years, and with that, the most common symptoms. In the past, lung cancers such as squamous cell carcinoma and small cell lung cancer were most common. These cancers tend to grow near the large airways of the lungs and cause symptoms early on—commonly a cough and coughing up blood. Now, lung adenocarcinoma, a tumor which tends to grow in the outer regions of the lungs is most common. These cancers tend to grow for a long time before causing symptoms, which may include mild shortness of breath, subtle weight loss, and a general sense of being unwell.

Diagnosis and Staging

A combination of imaging studies, including CT, MRI, and PET scans may be used to diagnose lung cancer. In addition, a lung biopsy is usually needed to determine the type of lung cancer.

Careful staging—figuring out how extensive a lung cancer is—is important in designing a treatment regimen. Non-small cell lung cancer is broken down into five stages: stage 0 to stage IV. Small cell lung cancer is broken down into only two stages: limited stage and extensive stage.

Causes of Lung Cancer 

Certainly, smoking is an important cause of lung cancer, but noting the statistics above, there are other important causes of lung cancer as well.

Radon exposure in the home is the second leading cause of lung cancer and the most common cause in non-smokers. Any home in the United States (or anywhere in the world for that matter) is potentially at risk, and the only way to know is to do radon testing. Radon is an odorless, colorless gas that results from the normal decay of uranium in the soil beneath our homes. It's estimated that 27,000 radon-induced lung cancer deaths occur yearly in the U.S. alone and that 15 percent of cancers worldwide are related to radon exposure.

Another 7,000 lung cancer deaths occur each year due to secondhand smoke. Other causes and possible causes include occupational exposures, air pollution, wood smoke, and cooking with poor ventilation. Recently it's been found that human papillomavirus (HPV)—the  virus which causes cervical cancer—is  associated with some lung cancers, though it's not at all certain if this may be a factor in the cause.

How Does Lung Cancer Begin?

Lung cancer usually begins several years before it causes symptoms and is diagnosed. Cells in the lungs may become cancer cells after going through a series of mutations which transform them into cancer cells. Gene mutations—or changes in the DNA of the cells—may be inherited (as a hereditary predisposition) or acquired (damaged as the result of exposure to carcinogens (cancer-causing substances) in the environment. This accumulation of mutations is one of the reasons for a common finding with lung cancer: Many people develop lung cancer though they have never smoked, and some people smoke their whole life and never develop lung cancer.

Lung cancer begins—a tumor originates—when a mass of cancer cells becomes immortal in a way; cells dividing and multiplying out of control. Our normal cells are regulated by a series of checks and balances.

How Does Lung Cancer Grow and Spread

One of the differences between benign lung tumors and lung cancer, as noted, is that lung cancer cells have the ability to break off and spread to other regions of the body. This spread, in fact, is the cause of most cancer deaths. One of the differences between cancer cells and normal cells is that cancer cells lack "stickiness." Normal cells produce substances that cause them to stay together. Without this stickiness, lung cancer cells can travel and grow in other regions, as well as invade nearby structures.

There are four primary ways in which lung cancers spread. It can "invade" tissues locally. Unlike benign tumors which may push up against nearby tissues, cancers actually penetrate nearby tissues. This is the reason for the name "cancer," which is derived from the word crab; cancer can send crablike extensions into nearby tissues.

Lung cancer cells can also break away and spread through either the bloodstream or the lymphatic system to distant sites. In recent years, it's also been found that lung cancer may travel and spread through the airways in the lungs.

Does Lung Cancer Ever Just Go Away?

Though it is very rare, lung cancer does, in some cases, just go away. This phenomenon is referred to as spontaneous remission of cancer. Researchers are tapping into this discovery to learn how our immune systems ordinarily function to remove cancer cells, and design treatments based on this principle.

Lung Cancer Screening

Until recently, we did not have a screening test for lung cancer, but that has changed. It's important to note that chest x-rays are not an adequate screening test as these fail to pick up lung cancers at a stage early enough to improve survival. Lung cancer CT screening is now recommended for people who:

  • are between the ages of 55 and 80
  • smoked for at least 30 pack-years (a pack year is calculated by multiplying the number of packages of cigarettes smoked daily times the number of years smoked)
  • continue to smoke or quit in the past 15 years

For people with other risk factors, such as a family history of lung cancer, a history of COPD, or other risk factors for lung cancer, screening may also be considered. It's estimated that if everyone who qualified for screening underwent these tests, the mortality rate from lung cancer could be decreased by 20 percent.

Where Does Lung Cancer Spread?

The most common sites of lung cancer metastases include the brain, the bones, the liver, and the adrenal glands. Some types of lung cancer—for example, small cell lung cancer—are often diagnosed after the cancer has already spread. Lung cancer is also somewhat unique in that it can spread to the bones of the hand and feet.

Lung Cancer Treatments

Treatment options for lung cancer have improved significantly in recent years. These include:

  • Surgery - There are several types of lung cancer surgery which may be done, depending on the size and location of a tumor.
  • Radiation therapy - Radiation therapy may be given as an adjunct to surgery, to decrease pain or airway obstruction due to a cancer, or in high doses to a localized region in an attempt to cure cancer (stereotactic body radiotherapy.)
  • Chemotherapy - Chemotherapy usually uses a combination of medications to treat lung cancer.
  • Targeted therapies - Everyone with lung cancer should have molecular profiling (gene testing) done on their tumors. Targeted therapy drugs are currently available for people who bear tumors with several genetic mutations including EGFR mutations, ALK rearrangements, and ROS1 rearrangements. Contact your oncologist for an updated list of mutations.
  • Immunotherapy - In 2015, two immunotherapy drugs were approved for the treatment of lung cancer. In some cases, these drugs have resulted in long-term survival even for those with the advanced stages of lung cancer.

A relatively new type of cancer care is termed palliative care. Palliative care is care designed to address the full spectrum of medical needs for people with cancer, including physical, emotional, and spiritual support. Unlike hospice care, palliative care can be used for anyone, even if you have a cancer which is considered curable. Early studies have found that, in addition to improving the quality of life for people, this care may also improve survival.

Alternative forms of treatment such as acupuncture may help people cope with symptoms that come with cancer and cancer treatments. These integrative treatments are now available at many cancer centers.

If You Have Recently Been Diagnosed With Lung Cancer

If you have only recently been told you have lung cancer, you are probably very frightened and not a little overwhelmed. Learning as much as you can about your cancer can help you feel more in control of your treatment, and help you play an active role in your care. Research your cancer. Reach out to friends and family and allow them to help you with things you can delegate. Learn how to advocate for yourself as a cancer patient.

You may feel isolated as you face something nobody in your group of loved ones can understand. Participating in cancer support groups and communities may allow you to connect with others who are walking a similar road. These groups are also a good way to stay updated on the latest research about lung cancer.

Take a moment to pamper yourself, and forgive yourself if you are feeling out of sorts. Nobody really knows how they will feel until they are diagnosed. The emotions you experience may span the spectrum from sadness to anger, to intense anxiety—sometimes in just a matter of minutes. Check out these first steps for when you are newly diagnosed.

If Your Loved One Has Lung Cancer

If it is your loved one rather than yourself who has been diagnosed with lung cancer, it can sometimes be even harder to cope. On top of the diagnosis, you may feel totally helpless as to what to do. At the same time that you are struggling with fears and sadness, the emotions your loved one is experiencing can be confusing and even heartbreaking. Check out these thoughts about "when your loved one has lung cancer" in which people who have lived with the disease share what they wish their loved ones had known.

A Word From Verywell

The face of lung cancer is changing. For many years, people living with lung cancer have had to cope with not only the stigma of lung cancer being a "smoker's disease" but the myth that it is uniformly fatal. This stigma is changing as the public becomes more aware that anyone with lungs can get lung cancer. The survival stigma is changing as well, as the public is learning of newer and better treatments that have recently ​been approved. In addition to the many new treatments approved in the past few years alone, there are over 100 medications being studied in clinical trials for lung cancer.

We still have a way to go, but many people are surviving—and thriving—while living with this disease. There is a lot of hope.


American Cancer Society. Cancer Facts and Figures 2016.

American Lung Association. Lung Cancer Fact Sheet.

Pass J, Carbone D, Johnson D. et al. Principles and Practice of Lung Cancer. 4th Ed. Williams and Wilkins: 2010.

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