lung cancer

Lung Cancer Overview

Lung cancer is a disease in which malignant cells form in the tissue of the lungs. As more of these cells are produced, they can form into a tumor and spread to the surrounding body tissue, lymph nodes, and bloodstream.

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Lung cancer is the nation's third most common cancer—more than 228,000 people are diagnosed annually. Beginning as an overgrowth of abnormal cells in the lungs, it can invade surrounding lung tissue and travel to other parts of the body through the lymph system and bloodstream. Treatment depends on the type of lung cancer someone develops—either non-small cell lung cancer (the most common type) or small cell lung cancer—as well as the cancer's "stage" (meaning tumor size, location, and other factors). Since cigarette smoking is the number one risk factor for lung cancer, the best thing you can do to tamp down your chances of developing this disease (and many other cancers, too) is to quit smoking or never take it up. Here's what to know about this lung disease.

What Is It

Lung cancer begins as an overgrowth of abnormal cells lining the airway or another part of the lung. It often starts in the lining of the bronchi, the tubes that carry air to your lungs. It can also develop in the smaller branches of the bronchi, called bronchioles, or the tiny air sacs at the end of those branches, called alveoli. Lung cancer claims more than 135,000 lives annually, accounting for nearly one in four cancer deaths among men and women in the U.S.


There are two main types of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), and each is treated differently. About 80% to 85% of lung cancers are the non-small cell type. Included in this group are adenocarcinoma, squamous cell carcinoma, and large cell carcinoma, although there are other less-common types as well. Lung adenocarcinomas (the most type of NSCLC) begin in the mucus-secreting cells of the lungs. It's the most common type of lung cancer in people who never smoked. Small cell lung cancer accounts for the remaining 10% to 15% of lungs cancers. These represent a more aggressive form of lung cancer; they grow and spread more quickly than NSLCs, and they're almost always smoking-related. There are two types of SCLC: small cell carcinoma (also known as oat cell cancer because of the small, fat shape of these cells under the microscope) and combined small-cell lung carcinoma (a rare form of small cell lung cancer). Whether the diagnosis is non-small or small cell lung cancer, treatment is highly dependent on the stage of the cancer.


Lung cancer can occur without any early warning signs and may be detected incidentally (say, if you have a chest x-ray for another reason) before someone develops signs of illness. Often, it's only after the disease has progressed to a more advanced stage that symptoms develop. Some people have chest-related symptoms, such as:

Sometimes, lung cancer symptoms are vague and non-specific, manifesting as constant fatigue or unexplained weight loss, for example.

If the cancer has spread to another part of the body, symptoms may be specific to that body part. Possible signs include:

  • Bone pain.
  • Headache, weakness, or other nervous system problems.
  • Yellowing of the skin and eyes (if cancer spreads to the liver).
  • Swollen lymph nodes.


Lung cancer is caused by genetic changes that alter the growth and function of cells. These changes, or mutations, can prompt healthy cells to grow and divide too quickly or proliferate without stopping. They can allow errors in the DNA of cells to persist without being fixed. Most of the time, these gene mutations are the result of lifestyle and environmental factors. The greatest risk factor is long-term tobacco smoking. Compared with a non-smoker, you are 25 times more likely to develop lung cancer if you smoke (but you can lower your risk by quitting). Other risk factors include exposure to secondhand smoke, radon, and asbestos. Other risk factors include:

  • Secondhand smoke.
  • Family history of lung cancer.
  • Exposure to radiation from radon, radiation therapy, or CT scans.
  • Exposure to certain metals and chemicals, including asbestos and arsenic.
  • Exposure to air pollution.
  • Taking beta carotene supplements if you are a smoker.


If lung cancer is suspected, your doctor will perform a physical exam and take your personal and family medical history to better assess your risk factors. A variety of tests and procedures may help to pin down a diagnosis. These may include:

  • Chest x-ray, CT scan, MRI, or PET scan, or PET/CT scan.
  • Bone scan (to see if the cancer has spread to the bone).
  • Sputum test (to look to cancer cells in coughed up mucus).
  • Needle or core biopsy (to remove and test cells for cancer).
  • Bronchoscopy (to look for tumors or blockages and collect a cell sample).
  • Thoracentesis (a procedure to drain fluid around the lungs; the fluid can be tested for cancer).


Treatment regimens differ depending on the type of lung cancer someone has, the stage of the disease, a person's overall health, and other factors. Lung cancer staging is based on a combination of factors: the tumor's size and location, the extent of the cancer's spread to nearby lymph nodes (the glands that help fight infections in the body), and the degree to which the cancer has traveled to other organs. A stage 0 non-small cell lung cancer, for example, hasn't spread beyond the cells lining the airway. It may be treated with surgery alone. More advanced cancers may require a combination of therapies. In general, non-small lung cancers are categorized by their stage (0 to 4), while small cell lung cancers are described as "limited stage" or "extensive stage."

Treatment options for lung cancer include:

  • Surgery.
  • Radiation.
  • Chemotherapy.
  • Radiotherapy (radiosurgery).
  • Targeted drug therapy.
  • Immunotherapy.
  • Palliative care.


Some risk factors for lung cancer, such as the genes you inherit, cannot be avoided, while other risks, such as those related to lifestyle, can be modified. When you consider that smoking is responsible for the vast majority of lung cancers, quitting smoking—cigarettes, cigars, and pipes—may help lower your risk of lung cancer. The sooner you snuff out your smoking habit, the better. Ex-smokers who've been smoke-free for a decade cut their risk of lung cancer by about half, compared with folks who've been smoking for the past 10 to 15 years. And if you don't smoke, don't start.

Other things you can do to lower your risk of lung cancer:

Avoid exposure to radon—a colorless, odorless gas formed when uranium in soil breaks down and accumulates in your home, often in basements. To check for radon, you can buy an at-home test kit or hire a professional to do the testing.

Avoid cancer-causing substances, including asbestos and arsenic.

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